Low Budget HD recording/editing PC

OK guys In short i want to start recording video from my xbox 360, and for this i need a capture card. I recently looked at the hauppage hd pvr and the blackmagic intensity pro, but don't know which is best. So for starters could you tell me which i should go for. Secondly I am going to need better specs to use these capture cards as i currently own a dell lapop with a single core @ 1.6ghz.

So my question is what can i do with 320 GBP. I do have 500 GBP but need to invest in a hd monitor/tv. Although i don't actually need to watch tv on it. It just needs hdmi and component really for the xbox 360 and capture card. Although i have already found this tv, if you can suggest a better tv or monitor that is cheaper and maybe even better then go ahead. What i thought about : http://www.ebuyer.com/product/158705 (Remember it doesn't need to have a TV tuner!)
IF THAT IS UNCLEAR AS THIS HAS BEEN TYPED QUICKLY AS I AM IN A RUSH I HAVE 500GBP TO SPEND.

Now for the PC: i already have a mouse and keyboard so no worries there I just need a computer build that can handle HD video editing in sony vegas pro 8.0. (The HD video will be from the capture card).

Thanks!

(Sorry about it being a little jumbled up I have written this in a rush)

build my new pc,
http://www.ebuyer.com/product/235763
http://www.ebuyer.com/product/147903
http://www.ebuyer.com/product/179183
samsung f3 1TB
9800gt (tbh, the onboard 4200 is fine, has hdmi)
good to go

Hmm, can you or somone else reccomend me a good Monitor please, as after reading that it has confused me as to what to look for in a monitor. I just need a good hd monitor that i can plug my xbox 360 and pc into at the same time and switch between them using the monitor. Also i want it to be full hd 1920x1080 and have a 16:9 aspect ratio. But I don't need it huge, just a 19" - 22" monitor or a little bit over maybe will suffice, i just don't know what to look for. Will check out the build you suggested now and see whether it is the sort of thing i want. Also i f anyone else posts other ideas I already have an OS -windows xp and windows 7- So that doesn't need to be included

EDIT:I found this it's cheaper than the other i found and highly rated on ebuyer : http://www.ebuyer.com/product/168144 does it look any good?

I just looked at the prices for the stuff you reccomended and it goes over my budget...
Basically for 500 GBP I need:
The computer
The blackmagic intensity pro http://www.scan.co.uk/Product.aspx [...] ce=froogle
The monitor http://www.ebuyer.com/product/168144

So technically i have 226.69 GBP to spend on the computer, which will only be used to record, edit and watch hd video. It does not need high end graphics just a graphics card that is known to do well when editing and watching hd video- but is obviously also cheap.