Good Enough PSU and large enough case for upgrades?

Hi guys I'm new to Tomshardware and had a question:
Will an OCZ Fatal1ty 550w PSU be able to power my build with these upgrades? (upgrades have the arrow)
i7-930 OC to 3.33GHz
Sapphire Vapor-X 5770 ---> XFX Radeon HD 6950 (planning on the BIOS hack to make it a 6970)
Corsair XMS3 (model#: TR3X6G1600C9) 6GB DDR3 1600MHz RAM (1674MHz, 1.64v) --->12GB same RAM same speed and voltage
WD Caviar Black 1B 7200RPM HDD (might get an SSD, probably OCZ vertex 2, and reinstall windows 7 x64 professional on it)
LG Blu-Ray Burner
Antec 600 Case with 2 green 120mm Antec tricool, 1 red antec tricool 120mm, 1 blue antec twocool (stock fan with case) 120mm, and 1 Antec tricool 200mm (stock fan with case).
CM Hyper 212+ --->push-pull with CoolerMaster Blademaster 120mm fans

PSU model: OCZ550FTY 550w ATX2V Modular PSU (with red LEDS)

Also, is my Antec 600 case physically large enough to fit the 6950? I'm OK with it blocking the top hard drive ports since i only have one hard drive mounted right now and that's towards the bottom...

Lastly, how well does the 6970 (BIOS hacked 6950) actually perform compared to cards like the 5870, 5970, 6870, and my current 5770? With BFBC2 I get some pretty substantial lag (even with 1xMSAA, 0xAF, HBAO off, and everything high @1920x1080) when i'm in (for example) a tank and the cannon fires right in my view putting off a huge amount of smoke and blowing something apart a fair distance away. The framerates drop for a few seconds to like 15fps and after the explosion slowly rise to about 25, then aafter about 45 seconds to 1 minute reset back to the 40-60 (vsync) i get during normal playing. Would the 6970 get this kind of lag? Sorry if I sound kinda noobish I don't really know much about video cards

Any help is appreciated

The PSU is fine for that.
The case should be fine for the card.
The card will perform the same as a HD6970 http://www.techpowerup.com/reviews [...] 70/29.html

I'm gonna upgrade it probably in the summer but I want to make sure now in case I have problems, here is the newegg link:
http://www.newegg.com/Product/Prod [...] xfx%206950

I'm planning on doing the BIOS hack in order to get the 6970 performance out of it

And yes I have a single 5770 right now I was building on a gfx card budget but now I have enough to get a new one. I don't want to go crossfire because the spacing on the Asus p6t motherboard is really bad for crossfire; the cards are practically touching each other (I could tell by looking at the second PCI-E x16 slot that the fan on the top gpu would be around 1cm away at the max from the hot RAM)...

a) With the 6950 won't need to overclock from what I'm hearing

b) Already have the case and Hyper 212+...case feels perfectly fine to me (significantly sturdier than my old Sony PCV-RX650 case) and the Hyper 212+ keeps my i7 at stock under 50C pretty much all the time, except during prime95 where it's topped out at about 52C...overclocked to 3.5GHz it stays under 65C even in Prime95 (and yes, i'm keeping it at stock once I get the new gfx card, though I have undervolted it both at stock and overclocked to 0.99v stock, and 1.137v overclocked so that should make a difference)

c) thanks for the suggestion...the RAM i have is now $80 and then there is a $20 MIR...I built the PC close to 5 months ago and I received the rebate for the 6GB i bought about 1.5months after I sent the application. Do you think $60 is a good deal (and worth it) for the RAM?
Link: http://www.newegg.com/Product/Prod [...] -_-Product

Yeah good idea...I'm actually gonna use an SSD upgrade to (1): boot Windows, and (2): install games...I'm thinking this is a good SSD looking at the reviews for it and it's in my budget, also, I've decided on either the 6870 or 5870 because I don't game enough to warrant a BIOS flashed 6950 which, as of now, only comes with reference coolers, and by the time there's a Vapor-X or similar model, AMD will probably have fixed the BIOS flash thing.
SSD: http://www.newegg.com/Product/Prod [...] -_-Product
Radeon 6870: http://www.newegg.com/Product/Prod [...] -_-Product (i'll overclock it XP)
OR
Vapor-X 5870: http://www.newegg.com/Product/Prod [...] r-x%205870 (little more powerful than 6870 from what i've read, but it's also $30 more expensive and the 6870 uses less power and I $270 looks worse than $240, if the price on the 5870 ever goes lower, then I'll take it...)
What do you think?
Oh yeah, and I'm not going to upgrade the RAM...at all