Hi folks,
Getting tired of Line 6 driver issues and will probably replace my interface. Need USB and am liking the Focusrite Scarlett 18i20. Looking for low latency since I play VDrums. Also considering an RME or  Tascam US-1800. Advice?

I'm reluctant to say you should or shouldn't buy a certain interface because I don't know how it will function with your equipment and circumstances, but I have a Scarlett 18i20 and like it very much.  I haven't had any problems with it yet, and I've been using it since they were first available.  It is my first USB interface.  I previously used Delta PCI interfaces.  Currently I'm using it with Sonar X3e, a Windows 7 64 bit, i7 system with 16 GB RAM.  I am using it with a Presonus Digimax FS through the ADAT connections, along with a DBX 386 through the SPDIF connection, and using the Scarlett as the master clock.  Everything works fine and I haven't had any trouble recording 14 tracks at 24/96 at the same time.  The Scarlett software is pretty flexible in setting up separate mixes for each performer, so I use that for low latency monitoring.  It works well, but if you need to use plugins while monitoring, you'll need to monitor through Sonar.  I'm a drummer and have used it with 14 mics on my kit, and also with an eKit that uses a USB interface.  I haven't had any problems with using the two USB inputs.  The preamps are pretty good.  I find them slightly cloudy in the lower mids compared to the Digimax preamps, and some of the outboard preamps I have, but they sound good and have enough gain to use with my ribbon mics.  One issue that is a minor inconvenience in my setup is the fact that phantom power is engaged in banks of 4 inputs at a time, so if you use a combination of condenser and ribbon mics, that could be a problem, depending on how many mics you need to use.
The instrument input sounds good and I use it frequently for recording bass. 
I haven't used the other interfaces you mentioned.

Aspenleaf,
Thank you so much for taking the time to give me such a detailed explanation of your experience. I really, really appreciate it! I will mark it as helpful once I'm using the full forum (on my phone right now).

Not to hijack the thread, but what issues are you having with the Line 6 drivers?
 
Also, just a heads-up...the AES convention is around the corner. It's common to introduce new pro audio products there. so there might be some other options on the horizon.

Being the proud owner of both a Scarlett 6i6 and a Tascam us1641 I will say with full authority, Don't buy the Tascam if you fear bad drivers. 
The us1641 is the older model, but I would hazard a guess the drivers share 98% of the code. The us1800 was more or less a face lift to the front panel. I would say go and buy it if all your going to use it for is tracking live drums. It's certainly the most usable inputs for your money. 
Tascam works real good for audio tracking, no problems, but it just would slowly get worse when you started adding soft synths and effects to a project. And it's not about latency, I'd say both the Tascam and the Scarlett are close with RTL.  Both are spot on for overdub timing. Both trigger MIDI with just a hare of delay. But there's more than that to audio drivers and how stable they are with Sonar. Focusrite Drivers likes Sonar as many will tell you. 
 
When you talk low latency don't be fooled by direct monitoring babble about zero latency. Of course it's zero because there's actually no latency involved when you monitor directly. There is no difference in monitoring latency between the Tascam and the Scarlett or any other interface for that matter. It's Round Trip Latency performance that separates the men from the boys with interfaces. 
It's when you monitor the output of the DAW while tracking that RTL will bother you. 
 
In your case, if you wish to track your USB drums while playing a VST drummer you'll need better performance. I have to monitor using my Yamaha DTX Drum Brain because it's much tighter timing for me. If I trigger a VST drum it's a 128th note but it bugs me. But the brain is using it's own USB drivers and so this might be a Yamaha driver issue, not the audio drivers. 
 
 Read this thread if you need to get a handle on what is good and what is bad about interface RTL, I bookmarked page 13 as that's more up to date charts. 
 
http://forum.dawbench.com/showthread.php?1548-Audio-Interface-Low-Latency-Performance-Data-Base/page13
 
 
I

Thank you Craig for chiming in!
You're not hijacking anything, I appreciate your help. I'm having clocking issues, apparently--clicking sounds during playback. When I check my driver settings, the UX8's control panel shows 44.1/32 bit although in Sonar, I have 48/24 selected and under Asio client the UX8's control panel is blank (not showing Sonar). Plus blue screens only when the UX8 is connected if I don't shut down in a certain order. Line 6 stopped supporting the UX8 years ago and the drivers were never great to begin with. We've had a good ride together, but I think it's time for a change. Don't think I can wait too long though, so might have to buy something that's out already.

I'm still in love with my Forte... rock solid, awesome mic pres, fantastic direct sound for bass/guitar, and way better deal than babyface... vocals are bliss.  Had emu 1212/focusrite pro24dsp/others... the Forte is a whole nother level of elegance and clarity...

Thanks, Sock Monkey!
I know exactly what you're talking about. The UX8 has direct monitoring and I know the difference (just like you explained). I've been able to play vdrums and trigger Addictive Drums 2 without any noticeable latency with my ux8. I'm pretty sure the Scarlett can be just as good if not better. Thanks for the info on the Tascam. I will stay away.

pinguinotuerto
Hi folks,
Getting tired of Line 6 driver issues and will probably replace my interface. Need USB and am liking the Focusrite Scarlett 18i20. Looking for low latency since I play VDrums. Also considering an RME or  Tascam US-1800. Advice?

I dont have that device but thats the one I plan on getting, hand down for me and my setup

Craig,
Just notice this interesting thing happening. 
If I open Addictive Dums 2 standalone, the UX8 control panel shows this:

 
If I open Sonar, the control panel shows that the UX8 is in sample rate conversion mode, and although this time is showing Sonar as the Asio client, sometimes Asio client is blank. Also with both AD2 and Sonar the UX8 control panel shows 32 bit although both programs are running at 24.