Best pairing of cpu+gpu (budget)

What you want to do is overclock your processor. It can get up to 3.3-3.5ghz easily just on the stock cooler.
As for the video card it is ok for your resolution but not particularly good. The best card within your budget is the HD5770. It will give you about a 20% boost in performance and DX11 compatibility but that's a lot of money for a marginal upgrade. I would save up some more and get a GTX 460 when you can. It is a good upgrade at stock and can also overclock a ton making it an even better value and very good for gaming at 1080p

if i left my cpu at stock speeds it still wouldnt bottleneck..say a hd 4870 or a 5770 ? as a gtx 460 is a bit out of my price range rite now.

if you have the motherboard for it and don't particular care for dx 11 you could always sli your 250 with another, that would be the best way to increase performance for the dollar, but as jyjjy you'd probably need alittle overclocking to get more out of whatever you choose

unfortunately my motherboard is somewhat old and doesn't support SLi, just curious if that extra memory (512gb to 1gb) and a higher tier would provide the minimum for 1080p gaming ( 4870 for $104 or 5770 for $130)

How much are you willing to dish out? HD5770 if you are willing to spend then you can go for it. But i would say that, it isn't much of an upgrade. You can get a better quad core processor if it helps.

ok i think i'm just gonna stick with my gts 250 and just run SC2 at medium/high @ 1080p and wait till early next year when the prices drop and the deals fly off shelves.

Basically you are asking the wrong questions. What you want is a card that is a worthwhile upgrade from what you have and that is good for gaming at your resolution along with a processor that is sufficient for current games. For the card what you want is a GTX 460. The 2 cards you mention will be better than the GTS 250 and are alright for 1080p but they are rather marginal upgrades over what you have now and are not worth the money you would spend on them. This is why you should save up some more for the GTX 460. Have you factored selling your current card into what you can spend? If not then you should be able to afford the GTX 460 already.
As for the processor you do in fact have one that is sufficient for current games just not at its stock speed. However it can easily overclock to be just fine. As long as you have a motherboard that allows you to do so then it is the obvious thing to do. This will help you whether or not you get a better card.

You're making a good choice, hang on to the GTS250 until the GTX460 1GB drops in price and/or you've saved enough for it.

ok thanks, now i need to figure out how to OC my cpu but i dont know if my psu/motherboard has voltage control. My motherboard is a ECS GF7050VT-M and i have a 450w raidmax psu. OC seems like the best option to get the most value.

Even if you can't increase the voltage I think it should still get up to around 3ghz or close to it.