Will 550 watts be enough?

550 can run no problem

'a 550 watt psu' - what brand/model? psu quality varies a LOT in the same wattage class and even within the same lineup (i am pointing at you, coolermaster and thermaltake).
and...550ti..? is this card for gaming @ 1080p resolution or general purpose?

It's an Antec 550 Watt, here's the link:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

and yeah I got the card for gaming at high resolution

the psu looks good. but, would you consider some thing like this:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
it has higher amps at the same price range. only setback is that it isnt modular. here's a review:
http://www.hardwaresecrets.com/article/881
as for gfx card, imo you could do better, considering the rest of your build. only if you haven't bought it already. if you've already bought the card, skip this part. for high resolution gaming, a gtx 670 would be better. if that's too costly, then a radeon hd 7850 might be okay. radeon 7850 is quite a bit more powerful than a 550ti.

Best answer selected by acg651.