One word of warning. The PS3 will only playback AVI and Mpeg2 files. If you have downloaded movies on Xvid, MKV or RMVB. You'll have to use a transcoding program on your PC to decoding those program before sending it to the PS3. I don't know if there is a Mac version of Tversity but you might need to dig around a bit.
Also. The biggest pain on the PS3 is that it does not come with a dedicated media remote. Unless you are comfortable using the game controller to control you media playback. You'll need to order this too:
http://www.newegg.com/Product/Product.aspx?Item=N82E16879261053
Haha, already have that remote in my Newegg wishlist! As for the streaming of movies, I have a few in avi/mpeg2 format already, but I don't see why I can't just play them off my MBP hooked to the TV directly with a DVI to HDMI cable.
Will probably be the best solution for me, but will definitely go the PS3 route. Thanks for your help and words of wisdom. Scouring the AVSforum for panel info as we speak!