Hardware and/or HDMI settings help please

Hello, I just finished my one week trial of ISBOXER to quad-box Diablo 3, and I am definitely hooked.

I posted this at the ISBOXER forum, but seems a bit dead over there, so apologies is some of you have seen this already:

I titled this with dual 750M Lenovo or single 770M laptop

Well, I am just finishing my week trial, but I am hooked and definitely want to play this way.
Current setup is Clevo D900F with 280M (desktop I7 920).

I can do the quad with lowest settings, 1600/900 resolution, main screen at 30/19 FPS, alts at 16/16, but I am only averaging 17 or so FPS on main screen. I assume this is the age I the GPU, and I had been planning to get a new laptop this summer anyway, but new to this so not sure what would be better? Desktop is not an option.

By the way, interesting observation last night. I normally play through the HDMI output to my project through the AV receiver, but last night I play on just the laptop screen.
I had a significant improvement in performance at the same settings, averaging about 25 FPS on the main with 28-30 most of the time except when heavy mobs or the initial casting of blizzard spell.
I am now back on the monitor, and even typing this message is now slow and there is a slight delay from typing to the visual (just paused the game to type this)

What gives? If I can get the same performance as just using the laptop on my projector, it is definitely livable for now.