Yep, I'd agree with Jasun and Jim. If you're going to buy a new computer then buy one, but don't buy it just for one game... Five years is a reasonable age to want to swap, and I think the more modern PCs will last much longer.
Every game, no matter how good/bad has it's knockers and it's pro-brigade, but the fact that now SH5 is available for only a tenner then it's got to be worth a peek, but only if your rig is up to it. Only you can then decide which camp to park your butt in.