1: Most should be quiet, the 7750 doesn't produce much heat but those with a large fan should be almost silent.
2: There may be a TINY loss of performance, a few percent at most, to all practical intents and purposes there will be no loss.
You don't seem to be in any hurry to change the card (no mention of it dying/died) so it'll pay you to have a bit of a hunt and see what turns up.
Like this:
http://www.frys.com/product/6639934?site=sr:SEARCH:MAIN_RSLT_PG
And it performs like this: http://www.techpowerup.com/reviews/ASUS/GeForce_GTX_550_Ti_Direct_Cu/
Be aware, this particular card is 'in store only' and 'check availability' .