You can always get an interface on loan to check out the latency on your system.  It is best to use a local dealer where you can take it back and pick up a different one the same day.  even if you have to pay a bit more.  Just make sure about the return w/ the sales man, preferably w/ a manager, too.  Virtual stores will let you do that too, but you'll pay more for the shipping if you do.
 
Differences in the same price range are always small.  A preamp on a $200 interface is not going to differ much between companies.  It is the drivers that matter, and there is no guarantee one model will work w/ your system - even RME (which most will acknowledge have the most universal drivers).  It should, but PC's are all over the place and one bit of hardware or software can interfer w/ the interface.  If you are worried about latency, trying before buying is a smart bet.
 
As to a stereo in, multiout unit, RME makes one, as does the Audient (which has their standard preamps, which are very good).  But those run about $700-800.  Presonus's stuff is good for the price - I've had a couple of their units.  Also note that if you plan on getting an external preamp, it is best if the interface includes line ins rather than just preamps.  You can turn down the preamp input to zero, but the signal still passes through the preamp circuitry.  Some people claim this hurts the sound.  I can't tell the diff, but you might.
 
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Issues of latency are most critical when you're tracking and your monitor/headphone feed contains live material. It's simply the round trip to the PC and back. This is why I prefer a unit with a built-in mixer so that the headphone mix can include the live material (mixed within the interface) and simply eliminate latency as a concern altogether. 
 
 

You guys are just fantastic! I was up till 5am reveling in my new system using my AK1... and now I wake up to your wonderful insights. I've reflected on them all before but you are truly helping me filter my own unique situation.
 
Super, I always love your whimsically relevant wit! My personal proclivity is that I never use the zero latency direct monitoring abilities which both my Saffires had. I'm an intuitive writer, building on beds as I create and feel stifled without everything impacting the next layer. I've tried to acquire exquisite vsts, like EW's spaces or guitar Sims which evoke my next splatter and zero latency monitoring just doesn't do it for me most of the times.  I like feeling the layers as I'm applying them, at least whenever practical. So, for me, latency is more important than for others who  can wield a more clinical approach.
 
AT...boy, you've done it again...hitting on several issues wonderfully. Buying locally...Absolutely, when ever possible I support our local guitar center in Emeryville, near Oakland. Over black Friday I was able to sit down all day with my own krk studio headphones (awesome,btw) and play 20+ basses and ended up with 2 Ibanez (4/5 strings) beauties that are just perfect for me, at a better price than anywhere else, while supporting their recent multi million$ investment in our community. 
 
I'm leaning towards the  presonus vsl44 right now as it has two mic/instrument and two mic/line inputs for an eventual outboard pre. Plus it has latency rivaling rme per  Jim Rosenberries' (?) recent posts elsewhere. I have no qualms about GC refunds/swapping as we're pretty tight.
 
And you're absolutely correct about being able to use it for a week to see if it's the one...Of course, having a backup plan just in case is also important. Some say the vsl line stutters at low samples like 64 which would totally change the latency equation but we all know, it depends on your system. I've invested everything in my new rig to eliminate the wussy rig complications. It's so awesome I'm just giddy with what I can throw at it!
 
Still, stumbling around is par for the course... I started running my AK1 at 32 samples to get latency down to 7ms and after a day off creating/working on getting comping down... I suddenly had system gridlock. Almost posted the issue, reinstalled kontakt which wouldn't load (well, it would over 5 minutes) and was freaking out, reinstalling things, to no avail when I read another post about ni loading issues and someone mentioned upping the samples... I upped mine to 64 and voila, smooth as silk again, 8 HOURS LATER...ARERG!)
 
Thanks all...I really value this process of helping me think this through and your generous giving of time to a fellow artist. I'm close to a trouble free setup now (although still got to move everything to my new noxiana deep silence case, which is unbelievable, btw) 
 
I love you...it's what wonderful about our community... and I'm close to the transparent song writing rig of my dreams!
 
 

another thing to consider as far as latency goes...
 
the more plugins being used, the more latency...
 
so, while i am in tracking mode, i do not do any mixing other than levels and pan.
 
i save even EQ'ing for mixing only, as to not tax the system, just keeps things cleaner as well.
 
so, if you find you have done an entire mix, and suddenly need more tracking, shut off all the plugins all the way across the board, including eq, and leave them off until you are through tracking.
 

Hey, batty! I luv bats, btw and they're in serious jeprody these days...
 
Absolutely... I understand this issue and generally start songs with basic beds if not just a single awesome synth/guitarz then begin vocalizing. That's when latency is most important for me. I find it helpful to create an ambience though, initially... too spur my creative juices...and even it comes to getting that pink Floyd guitar sound...low latency is a must as I can't become "the Floyd" otherwise!
 
If I add harmony later I do as you suggest, when necessary as what I have can defiantly wank even my luscious 4930.
 
It's a good point for all to remember... I first realized this back a few years ago using that convolution reverb cake has...it was ridiculous, and I had no idea I was creating my own latency problems.
 
I luv the button to deactivate all inserts. Oh, and to reactivate them too!

Super, I always love your whimsically relevant wit!

 

Just walked out of the newest, best Guitar Center anywhere (Emeryville, CA) with a PreSonus Audiobox 44VSL for the amazing price of $240, total price coming to $261.60.  Am awaiting some info on the Forte re: latency from Jim as I would truly love the RedNet preamps but some say latency is up around 10ms and that wont due...
 
If it comes out to be more reasonable, I'll probably jump ship; ain't opening the package for the audiobox!
 
I'll post some results later but am kinda excited at the moment as I was going to start with the 22VSL and save $110 to test it and then upgrade later but walked out with the surround capable version, 4 mic pres, two line in and 2 instrument ins, wall powerable to adequately handle my CAD E100S mic, and a bit better specs for $40 more!!!!!!!!
 
Moral: get to know and support your local store manager, especially if they're really into it like we are and you'll be happier than reducing transactions to webland!!!  
 
OK, gonna download latest drivers and give this puppy a spin!  Don't know if it's a keeper but got a few weeks to play with it and continue reflecting as they have lots of choices, including the Forte on their shelves...
 
YEEE HAW!!!!!

OK, I'm STOKED!!!!  Flawless set up, X3 loaded up a song I was muckin' with over the last couple days lickety split, unlike my NI Audio Kontrol 1, which was struggling and exuding long load times...
 
AND>>>> at 64 ASIO buffer setting, I'm getting..............................................................wait for it...........................wait...............................ok:

Glad you like it.  Good news.
 
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Very nice!
 
You know... this thread concerned me when I first saw it, since I just got my first Focusrite after rave reviews and you have had two of them die! Just gave the me "not good" feeling, but it has a feature I didn't even know existed until I stumbled upon it (ASIO aggregation)... and I cannot find that referred to anywhere! After learning about this, I will never buy another audio interface that doesn't have it. But you spooked me about it dying!!