2560X1440 and 1080P on a 2011 Mini?

I have a base 2011 MacMini with 8GB of Ram and a SSD. It has HD3000 graphics and I have increased the VRAM to 1024. I have been running a 24"1080P screen and a 22" 1080P Vizio TV that acts as a second screen when not in use as a TV. I purchased a Dell U2515H which is a very nice 25"1560x1440 screen with a USB 3.0 hub built in. This screen is perfect for my desk that sits in our kitchen.

Unfortunately, when I hook the screen up to the Mini (Dell supplied MiniDP to DP cable and Vizio through HDMI) I get intermittent, short blackouts on the Dell. When I tried using a MiniDP to HDMI adapter for the Dell I can't get 2560x1440. (I think this is a HDMI 1.3 vs 1.4 issue.)

I added the Caldigit Thunderbolt2 Station to give me USB 3.0 and eSata ports for my external drives. That also gave me HDMI 1.4 support so I could get the full 2560 over HDMI. That seemed to work for a while but eventually the Dell will either blackout and not wake from sleep while connected through the docking station with a MiniDP to DP cable or would give a garbled appearance with multiple vertical lines when connected with HDMI.

To confuse matters more, the Dell monitor seems to work fine if I run it solo. The problem behavior only seems to exhibit when the second (Vizio) screen is hooked up. The Vizio doesn't even need to be turned on just connected.

So I'm hopeful the a different screen will solve my problem but I'm concerned that the Mini really can't do 2560x1440 and 1080P at the same time. Or at least for more than a few hours before the graphics overheat.

Any suggestions for successfully running 2560X1440 and 1080P simultaneously would be greatly appreciated!

Thanks!