Worst case you can get a DVI to HDMI adapter for around $20.

I would opt for the 4x19". Even a 1080p LCD TV (1920x1080 res) would probably be painful. Each window will be around 960x540, and those pixels are going to be pretty friggin big. Whereas with the 19" each will be a relatively gorgeous 1280x1024 (if you can drive that res, 1024x768 min) and be much more pleasant when you have to read chat's or want to actually do something relevant (talents) on the alt.

The flipside is when you're not boxing the large LCDTV would be really nice to watch movies, etc. on.

Also keep in mind with the 19's that your desk configuration or eventual neck strain my drive you to verticle mounts which are additional cost. I highly recommend the verticle mounts as they help bring all toons into your field of view. Sure you don't generally have to watch those screens with much focus but switching around for looting, etc. can wear on you in long sessions.

Just my thoughts.