If you have three or more tuners (tuners as opposed to cards) in MCE you need to do weird registry hacks to get them all recognised. 2 is the normal limit. This applies to digital and analogue tuners.
MCE will also only let you use the digital portion of cards, to the composite, SVideo inputs are redundant, same with any FM tuner on board.
MediaPortal is about to move away from using Microsofts TV engine which has all these limits to their own that will allow a client/server system, all function of cards, and as many tuners you can squeeze in there. They are also speaking about enabling all channels in a multiplex to be watched/recorded at the same time with only one card. So in theory, with 6 tuners you could record everything broadcast on the UKs DTV system.
Encripted services are also supported. In MCE they are not.
Oh yeah, it's free and Open Source so worth giving it a try
http://www.team-mediaportal.com/