New system for around 400£

[yonk]

This system will be for all things, some internet, office, movies and of course little gaming too.

i3 2120
Gigabyte H61m-d2h
4gb ram
HD 6850
Xigmatek Asgard Pro
Corsair 500w CX2

This comes around 400£. I already have a hard drive. Is 6850 be enough for a 24" screen?

Can I a get something better for the price?

 

[yonk]

No new drives at the moment, but I am planing a SSD in a couple of months. Currently I'll have 2 SATA hard drives inside + SATA DVD rw, so will the Corsair orXFX 450w be enough?

And for the SSD, are the above motherboards suitable?
I'm still thinking about 4 or 8 gb ram, but that is easily bought afterwards.

 

[yonk]

On Asus Recommended Power Supply Wattage Calculator I got a value of 500W for this system plus 2HDD, dvd, dvb-s2 card.

Would be xfx 450w enough for this, or is the psu going to run on a very high load? Maybe a 550w or even 650w psu?
Oh, and I want a quiet psu.