Alot of games have all sorts of cinematic motion blur going on these days and i don't think you can disable it on consoles. Crysis 2 was unplayable for me with all the blur that was going on, luckily i'm on a pc so i just disabled it.
Sxrd's while 60hz had a wicked fast pixel response time (around 2.5ms) so you would want to find an lcd that matches that or beats it considerably to get rid of motion blur (if the blur isn't from the source material) Most 120hz lcds are around 4 ms response time while most 240hz are around 2ms response time, don't even consider the old 60hz lcds because almost all of them clock in around 6-8 ms. Plasma generally has a faster pixel response time especially in your price range, the only problem is finding a decent plasma with a good screen filter for daylight environments in that price range.
You don't list your viewing environment so i don't no whether or not the better black level performance of plasma or the better bright room performance of lcds will be a factor for you.
Definetly look for models with a game mode, all the extra processing that goes into 120hz and 240hz can slow things down to a crawl where input lag is concerned (input lag for you can be felt while panning/looking aorund in games where the game seems to lag behind your movements.
I'll provide a brief summary of some models for you:
Samsung un46eh6000 Great bright room performance, good screen uniformity due to full array of leds, decent response times, average black level performance compared to previous samsung lcds
Samsung un46d6400 An older model, probably still available in stores or online, deep black levels average screen uniformity and decent response times, 3d.
Samsung ln46d630 A stripped down older model which could also be a great deal, lcd for great uniformity vs edgelit leds, good black levels and bright room performance, decent response times.
Sony ex500 and bx520 I know another sony is probably the last thing you want to buy but they are probably the best bet for both good bright room and dark room performance.
Lg,Phillips,and Panasonic might have some very cheap 120hz lcds out there but you generally pay for it in the picture quality department, lg is probably the best of this bunch currently but also slightly more expensive than the other 2.
Samsung pn51e550(3d) or pn51e530 decent plasmas for the money, good black levels and great response times.
Panasonic tcp50u50 and tcp50ut50 (3d) decent plasmas for the money, great black levels and great response times would likely excel more in dark rooms. compared the samsungs.
lg 50pa6500 okay plasma for the money, likely average black levels and great response times. Cheapest 60" plasma i've ever seen is the 60pa6500.
You might be able to find some of these plasmas in 46" models as well.
Go look at some of these and figure out what you like, check the menu's on them for a game mode in store, pick a store with a good return policy as well as it's very likely that you won't be perfectly happy with the first purchase you make. Good luck