HD 5750 crossfired with HD 5770?

No, you are better of with 5750 crossfire, here a review of 5870&5850 mixed crossfire:
http://www.legitreviews.com/article/1107/8/

Quote "One thing that shocked me was that the CrossFire gaming performance of a Radeon HD 5870 + 5850 was lower than that of a pair of Radeon HD 5850 video cards in CrossFire in all of our testing with the exception of one game."

Definitely go for 5750 crossfire, and save the money, coz there will be no improvement, if you go for mixed crossfire.

With the price difference between the 5750 and the 5770 being so little - I'd skip getting the 5750 and go for a single 5770 now and then you wouldn't have to worry about it later when you get a second 5770 !!

Thats debatable, there is a powercolor 1gb 5750 for 105.00 free shipping today, 95.00 after rebate. The 1gb card will come in handy in crossfire.
Best Price Ever ! lol ends in a few hours.....another day,, another deal
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

thanks guys

No problem ^^