Your going to take an obvious resolution hit for PC games by not going through the Dell. With that said, I still highly recommend going large. Yeah, your Dell will always look better but I haven't met one person that doesn't get floored when I show them a PC, Xbox, whatever game on my 120" screen and 60" will have a similar effect. Also, It doesn't always work out perfectly for some PC games depending on your mouse/keyboard setup and I occasionally swap back to my 32" Visio in my PC room which is adjacent to my HT room.
LCD IMO is the best choice and while you don't specify a budget, the fact your rocking the Dell 30" suggests you can get an LCD. Regarding brand, do a search on AVS regarding game latency testing. There is a large, really large thread on all the brands tested. Some of them will cause lag from the sync between the video and you pushing a button on your controller.