I can't speak for Fohat, and I wouldn't say a single computer quad setup is unreliable as such, but I agree with him that 2 computers with dual-monitor setups has a lot of advantages. Adding a second computer and putting inexpensive dual-monitor cards in both (like the Matrox G450 or the ATI Radeon VE) provides redundancy which is essential to my peace of mind. Then, worse case scenario, if one computer goes down for whatever reason I've still got a fully operational computer with two monitors. Other advantages are you can easily network your two computers together to share data, backup data from one to the other, share broadband connections, etc. And these days a second computer doesn't cost much at all.