Transcoding: How powerful a CPU needed?

[sunray]

I'have a 2.66 ghz HT enabled EMT64 enabled Pentium 4 that acts as a media server and stores my Sage recordings, DVD rips and my MP3s. My HTPC has the capture cards (PVR-250s) and a 3.2 ghz Pentium 4 with HT but no EMT64. Both machines have 1 GB of ram. From reading the various posts in this forum it seems like you need a fairly hefty CPU to perform transcoding on the fly especially if you want to do other things at the same time. Does anyone have an idea how powerful a CPU is needed? Should I swap the motherboards between my HTPC and my media server? I have 2 MediaMVPs but I havent set them up yet. I'm still running Sage 2.28 but will switch to version 4.xx as soon as it seems stable enough for me. Thanks.