found cheap carbon fiber frame

hey i have a giant 2002 ocr3 (sporty) road bike. i am having the wheels upgraded (wheelset) to a shimano 16 (or 18) spoke aluminum pair from a 32 spoke entry level wheels. i've had the bike for about 5 years but have probablyput less than 75 miles (definitely a < 100) on it. i've just started cycling more this year (recently put 50 miles on it ) , and decided to do the rims.

then i get home and start poking around bike shops and find 9 carbon frames for $650. the frame weighs about 1780 grams (just under four pounds) and the steering frame was around 800 grams. Is that a good frame? it is a motobecane (one web-site called it a bogus bike, others said it was okay). i was told by a bike dealer that a carbon fiber frame is a carbon fiber frame, so i don't think the name should matter, right? i have noticed it is usually the components / extra stuff that chalk up the extra $$$.

btw ... i noticed that a 'pro' bike on another web-site only weighed in at 2.1 pounds, hence my question!
shrd

I can't speak for the Motebecane, but there are some pretty good carbon frames out there for roughly the price you mention. Check out these: http://www.pedalforce.com/online/ and be sure to go to the customize page where you can see the cost and weight associated with different component options.

-Dave

In this price range, the frames are usually made in Asia and then branded by the importer. This is true for Motobecane, so there is really no such thing as a "Motobecane frame", they don't manufacture anything, they buy the frames and paste their label on them.
1780 grams sounds pretty heavy. Looking at the Pedalforce frames gives me more confidence, the specs there looks decent enough for the price they charge. Furthermore, one of their frames looks suspiciously similar to a frame sold here in Sweden under a different brand name. Might be bought from the same manufacturer (in Taiwan, I believe) and I can vouch for that one being good value for money.