BS
Yeah you should be able to run Absynth as a standalone but I'm not sure if you would be able to run any other softs beside it. Vstack would provide you with a VST environment so you could use as many instruments and FX plugins as you can, and then be able to mix them.
However can I offer an opinion on your new PC. As someone who spend a couple of years fiddling with a PC I am very wary of non specofic PCs for music. That's why I've spent a considerable amount of dosh on a Carillon machine - still sitting at their workshops waiting on some of the more esoteric components I requested. So Ican't quite talk from experience but certainly the strong message I have received is that microsoft PC's struggle to do audio stuff unless set up properly. A dedicated machine will have had all it's components checked for stability and compatibility - it should work reliably and much more efficiently as well. Windows will have been tweaked to maximise it's ability to do sound. It will also have been rigged for silent running. Imagine a PC that makes no (or very little) sound. It will work out the box. For about 20% extra.
Dell still a good bet - you will get a reliable machine for a good price and given that in two years time processor speeds will have doubled etc the machine will depreciate in value so why spend extra on a dedicated rig, but then you could upgrade. You can get articles off the web to tweak windows, I might have some of these on my hard drive.
But I would say your best best is to go dedicated. Check out sites for Carillon, Millenium Music, Digital Village, Philip Rees and Red Submarine.
Ask John, he uses a Carillon.
Dave