I've been playing at 5k for half a year now and find UI size just fine (27" monitor). I don't need to squint and things look good.
http://i.imgur.com/Q3TsHCw.jpg
Why are people in such a hurry that mounts are needed in the fleet? Most players in my server are just lollygagging around GTN / cargo bays or jumping around in circles. Is a minute such a long time to run from one place to another and how many times do you have to run from opposite side of the fleet to another?
One thing I haven't seen in this guide (haven't read every reply) is the light/dark points gain. If someone chooses light side answer and others dark, what will the players get who don't win the reply roll? I hope I wrote that clearly enough...
It's also possible that the RAM upgrade caused the shared memory amount to change so there's now less video ram available. I'd check the BIOS settings.
edit: sorry, I didn't read XortiN's reply