I always felt like Sonar took a large hit in performance over the last year or so of its development. There was a point maybe 12-18 months ago - I think it was after Noel made some very worthwhile internal changes to the way Sonar handled synths - that I was getting absolutely stellar performance from it latency wise. Like you, never had to go above 512 even in very synth and FX heavy projects. For some reason though, it started going downhill and I'm at the point now where I have projects with a handful of instances of Reaktor in them and I'm having to bump it up to 2048 at all times, and even then I'm getting some crackles and pops (despite my CPU meters not even reaching halfway). 

To everyone here...My most sincere apologies. I'm humbled and glad you brought it to my attn. As for my response on this thread to your initial responses re Alesis.  I only meant to convey that I don't think Alesis deserves such a bad rap that it gets for having cheap equipment and that they have made what was previously very out of reach technology, VERY affordable, despite its shortcomings. Even after reviewing my last post, I don't know how I could have been more respectful, as I started it out "Well, with all due respect, and I DO mean that...." Also, I didn't necessarily complain about Sonar, I just said that I used the same setup that I had when it worked so well, and as Shark reiterated, he noticed a big difference in latency, and he's using VERY serious equipment.  So, I couldn't have been too far off the mark. And indeed, I DID try ASIO4ALL, and that proved to be worse than my Alesis, which is up to date.  They haven't updated that driver in years. Finally, as for asking for advice for shopping comparisons, all I said was "Penny for your thoughts." There are hundreds, if not, thousands of threads that ask the same question.  I didn't insult anyone; at least in the nasty vein that's insinuated. But I apologize nonetheless.

So, Shark, I was considering, troublesome as it might be, to upgrade my DAW to Win10 to see if that improved any performance.  The IT guy that services my PC's says he uses Sonar Platinum and when he upgraded from 7 to 10 he noticed a very significant improvement, but what's your take, if you don't mind me asking?
 

Asio4all is a desperation move if you don't have an interface. Does Alesis have a forum. Doubt you are the only one facing this issue. Also, have you checked other common performance issue triggers like drivers that compound latency? Sonar is unusable on my laptop due to crazy spike when wifi drivers are enabled

This may get you on path to at least knowing if it's interface driver:

http://www.resplendence.com/latencymon

Gee! THANKS! Dubdisciple.  I can't get to it right now, but will keep you posted.

Good luck!

All is good, I was only trying to convey how some of use who regularly help can get our dandruff up when certain people never reply to threads they start, just me and not a big deal really. 
 
And sorry if my comment about shopping for an interface sounds harsh, but it is true. Nobody but you would know what your requirements are. So the question about which interface to buy only leads to more questions like- how many inputs do you need etc. People are quick to recommend interfaces without really knowing what it is you need. Just because it's the right one for so and so doesn't mean it's the right one for you. 
Here's my handy dandy list with things to think about. You can skip the first stuff , but it's actually all relevant to your question. I personally believe your life will be better with a better audio interface. 
Otherwise your spending ( wasting?) time always troubleshooting and putting out fires. 
http://www.cactusmusic.ca/Recording.htm