Windows 7: recommendation for budget gaming graphics card

hello

what is the best gaming graphics card that i could buy for a price around £100 (bit more or less) bearing in mind the power supplier i currently have is a 400w power supplier

thank you

You are likely more limited by a 400W PSU than your budget. First check you vendor and sort by price, then check the specs for the one with 400W or less minimum PSU.
An nVIDIA 650 of some kind may fit you well.

Sapphire HD6670 OR 7770 since it is incredibly low power consumption, but I think the 7770's limit is 450.

I'm confused by their listings, but www.sapphiretech.com has one 7770 that needs a 6 pin PCI-E power connector and a 500W PSU. The other 7770s have no auxiliary power, and only require a 400W PSU.

I'm waiting for someone to invoke the conventional wisdom in this forum, requiring at least a 25% margin over the specified PSUs...

I would commend on the numerous 7700 series offerings, but the sapphire page is terrible and will not load for me.

But yeah, I think the one you are referring to is the flexible 7770 or something like that I believe it's called.
When it comes to the PSU, you are also right, it is recommendable to have some extra power laying around, specially if you do not have a good PSU.
I have the HD7770 Vapor X OC Version and the specifications on the very box says it requires at least a 430Watt PSU, so it is very confusing at times. Either way I have been running mine overclocked over the base OC on a 450Watt PSU and it holds great if you ask me.

Still planning to get a 550WSeasonc PSU in the future though, you never know when your PSU might stop outputting as much wattage as it first used to.

Bought Asus Nvidia GTX 650ti and it is working like a charm.. the whole PC is preforming way better that it used to do.. definitely recommended.

my previous gpu is ancient .. it was an nvidia 8600 gts lol

Be careful with that PSU please.
We don't want you to suffer a big economical loss.

how do i know if the psu is struggling with the graphics card.. cause everything is running smoothly so far

is there anyway where i could test the psu

A 640 is under £80 and is decent value.

Asus Nvidia GeForce GT 640 Graphics Card (2GB DDR3, PCI Express 3.0, VGA, 2x DVI-D, HDMI, Nvidia 3D Vision Ready): Amazon.co.uk: Computers & Accessories

Download, install, and run Furmark.

FurMark: VGA Stress Test, Graphics Card and GPU Stability Test, Burn-in Test, OpenGL Benchmark and GPU Temperature | oZone3D.Net

If that doesn't overheat your PSU, I don't know what will.

Be warned that if the power supply dies, it may also destroy any or all other parts of your PC that it powers.