5770 or 4670 for HTPC on 1080P TV

What is it you actually want from the GPU ? If its just HTPC @ 1080p then you dont even need a GPU at all, there are Motherboards out there with intergrated graphics that are more than capable of outputting 1080p quality images.
If you are looking to game a little then personally i would look at a 5 series card as its the newer tech.

Mactronix

Looking to view internet, OTA, and other source videos on TV as well as streaming to other sources such as PS3. THis will of cource require some encoding/transcoding. I know upscaling/trasncoding an such is cpu intensive, i just want to make sure that i have a sufficient GPU as well. Some of the charts show FPS ratings on cards at 1900 x 1200 being pretty low with anti aliasing and such enabled, is theis information independant of what i will be doing (applying only to games) or does it have something to do with viewing upgraded content on a 1080 TV. On the AVS forum it states that the GPU is important for viewing and encoding, but also says you reach a point of diminishing returns. On all the midrange systems AVS recommends the 5670 and goes up to the 5750 on its higher end stuff. THere does not seem to be much good talk about the 5670 while the 4670 is highly praised for its value and is often out of stock at newegg. The 5750 is so close to the cost of a 5770, its seems stupid to buy it instead. MY thought for a possible system included the following options:
I5-750/Gig h55m ud2h with 4670 or 5770
i3 530/Gig h55m ud2h with 4670 or 5770
630/Asus m4a77td with 4670 or 5770

Will i5 improve transcoding/picture quality or just speed
Will 5770 improve transcoding/picture quality on TV or just GAMES
Is anything gained by getting a 4670 over the igp for either the i3 or 630

Im by no means an expert when it comes to HTPC's but know the HD range of cards do take the load from the CPU and have hardware decoding which will help you.
The direct compute on a 5 series card could well be a big advantage but i dont know who supports it as of now.
From what i do know i would recomend you get an i3 teamed with the 5670.
That gives you a very capable CPU and a capable entry level gaming GPU should you fancy it. I dont see the point (unless its a price thing ) in getting a 4670.
The i5 750 would help if you was looking at gaming as its native quad cored i beleive.
So an i3 and a 5670 would give you a bang upto date PC which would be suited well to what you want and could game a little if you wanted.

Mactronix

Are you playing any games? If not then the HD 5750 / HD 5770 is a waste of money.

The HD 5670 is considered "bad" because it's current price point does not justify the gaming performance that you get. The advantages of getting a HD 5xxx over a HD 4xxx for HDTV purposes is it's now possible to have 7.1 channel lossless sound 192kHz / 24-bit. The HDMI audio output follows HDMI standard 1.3a and now also supports Dolby True HD and DTS-HD audio. Of course, to get all those channels you will need to connect the HDMI cable to an audio system and have 7.1 speakers.

There are 512MB and 1GB versions of the HD 5670. If you are not gaming get the 512MB version. The 1GB version for playing video is a waste and costs about $10 - $20 more.

I only have two speakers in my audio system, so THe DTS thing is no big deal for me. My concern is with the video encoding/transcoding ability of these cards. If DTS is no big deal for me, does that change your recommendation. What do you think about CPU's. EVerything i have read says that a quad core is better than a dual, so i was leaning torwards the two quad selections above. What do you think.

THank you both for your input on all these questions.

I wouldn't bother with a GPU's ability to encode videos. It is still in it's infancy stage and the program you use must be able to access that particular capability. Video encoding is still solely dependant on the CPU in my opinion.

Quad core is better for encoding purpose as it will cut down on time as long as the codec you are using supports that many cores....

DivX -> Don't know about the current version. Version 6.xx supports dual core, but not quad core.

XviD -> Dual core support. Quad core, I think not.

x.264 -> Definitely does support quad core. Due to the "slowness" of this particular video codec, I recommend the fastest quad core you can possibly afford to buy. Doing a 2-pass encode of a 2 hour movie @ 1920 x 1080 resolution is ridiculously slow. I estimate a stock speed Intel i7-920 quad core CPU will take about 12 - 14 hours to encode a movie. Enocding 2 hour movie @ 720p resolution would probably take about 4 hours using the 2-pass mrthod.

If audio bit streaming is not important, then you can drop down to a HD 4650.