I pulled the trigger on the Mac Pro cheese grater. After a very long comparison, I ended up getting a 3,1 2008 dual quad-core 2.8GHz Xeon with 10GB of ram, 320GB 7200rpm HD, ATI Radeon HD 2600 XT 256MB.
It runs VERY smoothly on 10.8.5, but I'm going to try to go up to El Capitan and see how it handles various video editing solutions. I also have an external 1TB WD I am throwing in. I have a Blu-Ray drive I'd really like to put in, but it's SATA whereas the 3,1 seems to be only IDE for optical drives. Is there an adaptor solution?
EDIT: Well, this is fun, it's asking me for an admin password, the salesperson didn't give it to me, and I didn't think to ask. Herp derp.