Used MacPro Student purchase ideas?

[Kelisdad]

almost 2 years ago to date I asked this forum for help with a MBP for my daughter working on her degree in graphics. As a result I got her a 2013 15" 2.3 i7 and it's worked out wonderfully so far. She started motion graphics this January so we added the 27" TB Display to her arsenal.
Now my query, I'm going out on a limb here in guessing motion graphics probably would benefit from more horsepower - say an 6, 8, or 12 core CPU? So I'm researching used MacPros that I can upgrade for her.
Here's my checklist:
CPU unit < $700.
preferably upgradable to utilise multiple displays including TB Display
I can do the processor upgrades myself, so I could use some guidance as to a "sleeper unit" I can drop a higher quality chipset in.
Graphics CPU recommendations.
HDD set-up?
Currently, she uses Adobe's CC and her MBP for her projects which meets her current needs.
I want to reward her hard work with a machine that will hopefully enable her to increase her "skills" level even more and then take into the work a day world when she's ready. I'm in no position to buy a TrashCan from Apple for her. I do however, have an abundance of used Quads and Octos for sale around me on the used market. Prices range from $400 - $750 for lightly upgraded to base machines.
Ideas?

 

[MacVibe]

Getting her "more stuff" to mess around with sounds like a distraction to her working on her course work. If a time comes in the next few months when her very capable i7 MBP (4 cores plus hyperthreading for a total of 8 threads) is not able to keep up with her assignments, I suggest asking the instructor (or program director) what sort of hardware students are typically expected to use for homework and projects.

 

[chrfr]

CPU unit < $700.
preferably upgradable to utilise multiple displays including TB Display

Only the 2013 Mac Pros have Thunderbolt and there is no way to upgrade an older one to use the Thunderbolt display.
As someone who works for an art department at a university, I'll echo the idea that your daughter should focus on the work and not the hardware. Her laptop will be more than adequate for the vast majority of work she's doing, and if it isn't, the school may have other options for her to use on the rare occasion she needs something more powerful.

 

[Kelisdad]

to clear something up.....

first, thanks guys for your thoughts.
My daughter has no idea I'm researching this build for her. She is laser beam focused on her education. If her Mom's second round of battling cancer has not got her off kilter, my surprising her with a gift probably won't. She has been working in the graphics department on campus since transferring in and when she's not in class she's working on her **** load of projects. I kid her about how focused she is on her work. I tell her she can't help it, it's in our DNA --- we tend to get tunnel vision when creating something. It's in our genes. So don't stress it, just go with the flow. We tend to get very intense in our creative moments.
I guess because I'm so damn proud of her. I observe the blood, sweat and tears that she pours into her work and want to help shoulder her burden! I just want to do everything humanly possible on my end to help her to succeed.
I know, she's got a goofy Dad!

 

[Kelisdad]

and the TB Display

I gave her the Thunderbolt because she was trying to get her 17" iMac G5 from high school to work as a second monitor off the MBP while working on her very first motion graphics class assignment and in frustration finally gave up. Never said a word to me about it but when I stopped by her mom's house, she(ex-wife that is) told me all about it (in a good way). She comes home one day every weekend to be by her mom. So next visit Mom sent her over to my place to drop some baked goods off for me and BAM! Surprise! here you go, think this will work a little better than the G5?