In the Dell dual-Xeon choices, I much prefer the T7600 as it is much more expandable in the drive area (up to 8 drives, 4 x 2.5" and 4 x 3.5") and really does not cost too much more. It also has more room for expansion cards, slots for numeraous RAM possibilities, and a beefier power supply.
Also, I would strongly suggest upgrading to 32GB of RAM; Adobe will use a good bit, plus Win7 64-bit is pretty effective at using what your apps are not for drive caching. Dual Xeon Dell's also seem to like 8 sticks of matched RAM.
Hopefully your college's policies will let you purchase a video card on a separate purchase order!
The Quadro cards are overpriced!
The nVidia GTX cards work very well with Premiere Pro, which seems to love both the # of cuda cores and memory bandwidth. Good video choices include:
GTX 680 - for $500, it pretty much provides the same rendering oooomph as the K5000 (same # cuda cores, GTX has slightly faster memory throughput)
GTX 780 - around $750, this would be my choice - fast, fast, fast!
GTX Titan - around $1000, faster still; I am currently playing with one in a T7600 and the DVD render speed is amazing (2688 cuda cores, 288.4 GB/s memory vs. 1536 cores / 173 GB/s memory for the K5000; K2000 quadro has a measly 384 cuda cores and 64 GB/s memory!!!)
If you can buy "non Dell" parts, and you go with a T7600 solution, then adding some for 1TB or larger 7200rpm 64MB cache drives would be a good idea as well. Unfortunately, Dell seems to charge too high of a premium for the same drives you can purchase at Newegg.
I agree with Jim.
I got the T5400 some years back, and it was quite limited with expansion fdor drives, but it still runs fine, though. If I were to get another one today, it would for sure be T7600 because of the space.
Dual 2000s won't help in editing since you can't combine them. The k5000 seems a good choice (I have the mobile edition), but whether you need the precision is a decision you will have to make on your own.
Unlike GTX (gaming cards) Quadros are certified to be stable and accurate in a variety of applications including Adobe products. Since this is a school where wear and tear will be heavy, I recommend the pro card variety.
One more thing you should know, the updated graphic cards from Nvidia (K5100) are about to be released so you many want to investigate whether or not those cards are available yet. At double the GB capatiy (8GB vs 4GB) its well worth waiting for.
ps. You will also need a RAID array (for HD) and also get a blu-ray burner. At only a couple hundred dollars it wont' break the bank and at least one of your students will thank you for it.
The Failure rate on higher end Geforce cards is extremely low. It's actually lower than the Quadro cards. Since they have better performance by far especially with the Titan and the ram space of 4 to 6GB I would not look at a Quadro without a 10bit color workflow.