The Roland unit is a great. The in built features and effects are great but I'm not sure about spending another thousand plus dollars when you already have a great PC setup. Go get a good sound card and a sequencing software and you are in action.
If price is not a consideration then I think the difference is in the ergonomics. You should try to get a sequence software demo (like the Cakewalk) and use your existing cheap soundcard to do some trial recording and mixing with it. If you like how it works, there you have it .. maybe the grass may not be a lot better on the other side. But if you hate how it works, consider the Roland unit. I think its a great unit with great in build features.