If you're particularly interested in high definition I wouldn't even consider the Denon A1XV if I were you. You should get a stop gap DVD player until next year when Blu Ray and HD DVD come out, then you should buy a combination Blu Ray / HD DVD player. That will maximise the enjoyment period you get before having to buy something else. The current crop of high end DVD players are fine if you're got a high end projector and want to optimise the source now or you have a big collection of DVD's and don't plan on jumping on the high definition bandwagon straight away. The problem with the Denon A1XV is you're paying a huge premium for it's deinterlacing, scaling, and noise reduction abilities and these technologies age rapidly so after 3-4 years your big heavy Denon is still built to last but has outdated technology locked inside. Opting for a cheaper DVD player and hot of the press video processor combination as Gandley suggests makes much more sense. I would agree with Gandley again that if you go for this option you must get a player that outputs 480i over HDMI because that will feed the video processor a pure digital signal that hasn't been messed around with. Video processors like pure unmessed with digital signals. They will do a better job deinterlacing and scaling the image than most DVD players will. A cheap alternative, which will arguably produce an even purer digital signal for a video processor is to get a mid range or budget SDI modded DVD player and mid range SDI modded video processor. Have a look on crtprojectors.co.uk for more information on SDI modded DVD players.
Gandley what's you view on HDMI 480i Vs SDI 480i. Are they exactly the same quality? I've just ordered a Marantz DV9600 which can do the same as your Pioneer with 480i over HDMI and have just sold my SDI modded Philips 963SA which produced a stunning picture with an SDI modded iScan HD+, so I'm hoping to at least match the SDI combo picture quality. I don't think I will better it. I have a Marantz S4 projector so I can either use the ABT scaling in the DV9600 or the algorithm upgradeable Gennum deinterlacing, scaling and noise reduction in the S4. Have a look at this;
http://www.marantz.com/pdfs/e_dv9600.pdf
Any idea what deinterlacing chip the DV9600 uses? I can find it anywhere. I'm assuming it's the same SIL-503 chip used in DVDO's video processors.
Ricky good luck with whatever upgrade you choose.