The XL systems was thought as HTPC, and so I think there will be no problems about HDDs heat - infact, in some models there were two, one on top of another, and I heard about no issues about HDDs heat problems, and those models are 6/7 years old... plus, newest HDDs should produce less heat than older, in particular 5900rpm models.

Yes, GPU should be low profile; in particular, the AMD based HD 5450, 6570, 6670 and 7750 are the ones tested by many XL users, and all works very well; as the PSU is only 300W, their power consumption is well under their specs, around 50/60W. Still, don't know a lot about Nvidia GT640; it's a new card for "us" XL owners, and should be tested further, but I think it will be OK, too.

And there should be no problems for PCI cards, as they are horizontal and with some empty space between the PCI riser and the PCI-e slot.

RAM: a heat spreader is welcome, but as the max speed is "only" 667MHz for 8GB, and 800MHz for 4GB, I don't think it will be "crucial".

The Esi Juli@, after many research, seems the best price/quality sound card, with RCA input so needed for movie captures; the LynxTwo is better, but will cost 5x, so...

I'm still looking for the best PCI video capture card with a good comb filter... I like very much AJA products, but it seems they have only a three-line comb filter. I'm still looking further info of the comb filter of the Osprey Viewcast PCI models, but without success. The ATI HD 750 seems a logical choice, but as this is only PCI-e, and I have only one PCI-e slot (for video card) I can't go for it, and I'd like to avoid any USB capture card.

Or, as my capture card is quite good, apart comb filter, I should find an external device with a very good comb filter; the best one should have a 3D filter that works with PAL signals too!