I don't think the version of Sonar is the issues with underpowered computers. It's possibly more a case of compatibility with audio drivers and OS. Then certain versions were more stable and bug free than others.
I've used Splat on a very low powered 2008 Sony laptop with 4 gigs Ram. But it has a SSD which is probably important for larger track count. Ram is important if you start adding plug ins and VST's. The processing speed is not as important, it just get things done faster but they'll still get done no matter what..
I recorded 16 tracks audio and 1 midi track hours and hours , gig after gig on that machine.
I bought Home Studio to use for this and live playback. It's certainly rock solid no frill and it's way more up to date than if I used 8.5 which now seems a waste of time using to me... I used to love that version.