Yes, I too previously was using my external tv tuner with 15" CRT monitor. But after bringing this LCD, my tv tuner card didn't worked. So I bought Umax Tvision external tv tuner card, and I am watching tv on 1440 x 900 resolution on the same LCD.
And yes, I am also using RF cable. (Dish tv) And no degradation in quality. You just need to buy a new tv tuner supporting atleast this resolution. My tu ner supports maximum 1680 x 1050 resolution, but still I use 1440 x 900 resolution, I feel that right. You'll need to experiment according to your choice.