I have decided to make the switch from my old but decent Compaq Pentium 4 machine to a brand new Lenovo Dual core machine. Main reason is to get flawless 720p playback and better support for 1080p video. My LCD only handles 720p/1080i but its good to know that the box can playback anything smoothly.
I choose the Lenovo because of the 1.8ghz dual core processor and full size PCI slots. Other machines I have looked at have had half size or low profile PCI slots and to be honest after all the hassle getting the graphics card for the last one, I'm not willing to do it again. The Lenovo has intel graphics (which seem to be accelerated and are open source) which play well with Ubuntu but I was worried about the OpenGL 2.0 support. So far it all seems to be ok. I also gave the new machine a serious upgrade in memory and space. From half a gig of DDR to 2 gig of DDR3 memory.
Upgrading has been a pain. I took the 5.1 PCI sound card out of the old machine and switched it into the new one. Installed Ubuntu 7.10 (didn't have 8.04 cd) and upgraded to 8.04 over the internet before installing XBMC 9.11 alpha. I had to fight to get the display working correctly when the display defaulted to 1360×768 by 60Hz instead of the 1280×720 I wanted. Rather just living with it, I decided to mess with it and got to a point where the display wouldn't show anything. Unlike a normal computer monitor, LCD TV's tend to throw a message up saying not valid signal, which is no use when your trying to work out whats happening. Anyway I got it working and before long was installing XBMC and Boxee. I had previously backed up my XBMC, so once I SSH'ed in and moved things back I was up and running. Next step was the audio which is fiddly because of my setup using the Onyko Cinema Amp. After a long while I setup Ubuntu to output audio over my Cmedia PCI/DNA card, disabled Pulseaudio from starting by changing /usr/bin/pulseaudio to non executing and trial/error in XBMC till it worked. Now I can play Dolby Digital and DTS without a problem. Oh and here was nice bits and bobs which might help with getting a better xbmc experience.
I did some tests with some 720p content I own, and I was shocked at the cpu usage. One CPU core bearly touched 40% and the other one was almost idiling at about 5-10%. When pushed into sub 1080p content (1440×1080) the 1st core touched 50% but never went over it, likewise the 2nd core almost sat idle. All my 1080p content seems to wrapped in a MKV container right now, which currently seems to crash XBMC at the moment. Quicktime also seems to have the same effect currently. I'm sure upgrading to the beta will solve the problem. So far, I'm impressed but my next step is to file some bug reports around MKV files, get XBMC to launch from login like I use to have it an finally autostart with the wiimote