The 24s are a LOT more monitor than 22s. 24" have 1920x1200 and likely either a PVA or MVA panel. 22" have 1680x1050 and likely a TN panel.
Not really necessary. 8mb RAM per port is plenty. Years ago I ran multi-card systems with 4MB ram each with no problems.
I would just add that make sure you have a motherboard and a power supply that can handle this too. If you don't have a high powered of the 2 you will have issues. I can't for sure tell which mother board to consider, but you will definitely need a power supply greater than 850 at bear minimum. I ran the NVIDIA NVS quadro along with a GeForce FX card running 6 moni's on a Dell Workstation and fried 4 motherboards and 2 power supplies. I had a 650 power supply, but I can't remember what my mother board was. Sorry. If you accommodate for these you should be good to go! If need by request I can try to go into further detail with my research and personal experiences. Good Luck!
Most modern P4/Athlon CPU and higher computers can handle the charting of 8 screens easily (possible whiplash from following the cursor across that many screens is another matter)... however, certain *applications* can overtax a system.
Of course you want to have PSU which can handle the load. However, the NVS 280 uses only 12 watts, the 440 (quad, PCIE) uses only 31 watts. A BIG PSU is not necessary simply because of the NVS cards...
Oh, of course. Not sure about this, but I don't think the number of monitors has any power impact on the mobo and therefore neither the PSU... only the video card impacts the mobo/PSU.
something else to consider. if you're going to buy 8 x 22's @ $300 each = $2400 + tax and shipping. I would strongly urge you to consider looking at the Dell 30". For the same price, you can buy 1 x 30" and 3 x 22's. The 30" is well worth it. I have a 30 running next to the 22's, and the 30 is so much bigger. It's also much sharper than the 22's. Of course, with the 30", you'll need a video card that can drive it, which will cost you about $90 for a geforce 7600 series at newegg.