One: don't expect "night and day" differences between your current setup and another budget setup. Drivers, compatablity and other such housekeeping items are the real difference.
And until your ears are trained - not musically but engeneeringly - you are no likely to have a night and day epiphany once you get over the fact you are on a great system. I don't know your situation, but it does take time to develop your engineering sensiblities, just like learning to hear your trumpet or any other instrument.
Finally, there isn't a night and day difference between high end and low end hardware for most listeners. The SOS test Jeff references is a good example. I've done similiar tests but w/ mp3 files (the unfortunate standard for listening these days tho it is pretty good too!) and couldn't tell much difference in preamps over compute speakers. We buy expensive stuff to make our job easier and confident since we don't have to second guess whether it is our chops or the equipment that is making the sound suck. If you have a UAD strip you run the bass through it because you have done it a thousand times and it sounds good and just works. If you have api you run the drums through it because experience tells you it works.
The one thing the SOS test missed was intentionally driving the preamps so you get a little hair on them - specific sounds that we know work, too. A generic, scientific test just doesn't bring out how artists use the equipment. Under many circumstances, a interface preamp will sound about as good as the most expensive preamp. Under certain circumstances the engineering artist uses it won't.
Buy the best you can afford and learn to use it. Upgrade components when you can. Learn to use them to your advantage. As your collection grows so does the ability and ears to use it specifically. Record music while you learn. Be happy.
I'd go with the Roland - many seem to like it and it works out of the box mostly and it should be a good match for Cakewalk by Roland. I've heard of more problems w/ the tascam/Sonar, tho I still have some of their analog hardware.
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