You need at least a line doubler. CRTs with tighter focus will require at least a tripler to avoid visible artifacts. If you sit close to the screen with a 9" EM focus projector, 960p is preferable if you don't get your focus off.
As far as mounting, IMHO table mounting is not a viable solution for CRTs. Throw distance almost always means that whichever side of the defacto standard 1.5X screen distance you sit, you must be off center in order to accomodate the projector or move far enough back that the screen is just a big TV. Most of us wouldn't be spending substantial sums of money on home theaters if we were satisfied with a less-than-optimal experience.
New Quadscans are less expensive than decent HTPCs (I'd have saved $500 if I went that route), don't suffer from DVD navigation problems (I can't get through Avia running Theatertek with the set of drivers I have), don't suffer from wierd PC hardware interactions (I have an Athlon XP1700, ATI Radeon 7200, M-audio 24/96, and Elite group main board (the ASUS I bought was defective) - not bottom of the barrel crap. It requires a hard power cycle following any warm reboot. This is anoying, but not a real issue), and don't have driver issues (with the CDs shipped with my hardware, netcape would often cause reboots). If you don't require the best moderately priced video processing and/or other HTPC functionality (I wanted to rip my CD collection in a lossless format), avoiding one might be prudent. If not, exactly duplicating (same software, drivers, hardware) a known working system is the way to go.