which to buy?

I am having a hard time deciding which would be the best fit for me. There are so many different options and I'm not sure exactly just how one unit is better than the other. I hope someone can clarify things for me. I'm looking at 3 units:

1) Mac pro 2010 - Intel Xeon Quad Core: 2.8 GHz Memory: 3 GB MC560LL/A Hard Drive Capacity: 1.02 TB apple warranty to 2014 - $1700

2) Mac Pro 2.4 GHz x2 Intel Xeon Quad Core MC561LL/A Memory: 6 GB Mac OS X 10.7, Lion Hard Drive Capacity: 1.02 TB No warranty but many Adobe apps CS5, premiere pro
- $1675

3) Mac Pro Intel Quad 2.66 GHz Nehalem 2009 MB871LL/A - Memory: 3 GB 2 Internal HD's (640 & 500) 1 external HD 1TB - No warranty $760

**All prices are at current ebay price with 2-3 days to go on each.

I will mainly use them for Video editing FCP 7, photoshop 5 and after effects 5 (most likely not at the same time, as I'm just learning A.E.) Any suggestions would be greatly appreciated

G'day and welcome to the forums.

Geekbench tests, which are basic, supply the following informqation for the various models, higher rating best.

2.8GHz 8,839
3.4 dual 12,942
2.66GHz dual 14,458

Ignore the software installed as it will be useless without the original software CD and activation codes and may well be on the machine illegally. For your needs current memory is barely sufficient.