That would depend on the specifications. I am going off the HP.com links to answer your question, but feel free to correct me if your specs are different:

IQ526: http://www.shopping.hp.com/product/rts_desktop/rts_desktop//3/storefronts/NC7...
IQ804: http://www.shopping.hp.com/product/computers/desktops/IQ800t_series/rts/3/com...

Really, it all depends on what your needs are. The IQ526 has a larger hard drive (640 GB vs 500 GB), but it does not have a TV tuner. The IQ804, on the other hand, does have the TV tuner. Other than that, from what I can see the units are identical. Myself, I would probably pick the 804 because it's cheaper and you get more for your money. I have an IQ506 and haven't had any problems with it-- not sure if that is any kind of reflection on the 500 series vs. the 800 series, however.

Unless things have changed, the 500 series is capable of 8 gigs of RAM while the 800 series maxes out at 4. I was a bit disappointed in that as I have an 800 series. My 800 sereis came with a 750 gig HDD and a TV tuner as well as a blueray DVD player that also burns CD's and DVD's but does not burn BlueRays.

David

http://i99.photobucket.com/albums/l299/xz550rj/HPMagicGiveaway.jpg

Woohoo! I won my Touchsmart!

GeekTieGuy said: If physical size is a concern because of where the unit is going to be placed, that might be a consideration as well. The IQ804 is much taller than the IQ526. In addition, the IQ804 can be wall mounted with an accessory (third party) whereas the IQ526 can't. The IQ804's feet can be easily removed for wall mounting. The IQ526's feet can't (not easitly, anyway).

A wall mount option for the 5xx series...

http://www.iversal.com/