Cheapest way to upgrade a system???

Is there a cheap way at the moment? I was checking out upgrading my PC from the i7 920 to a i7 2600 now that the new processors coming out and was still surprised to see costs high. As an example, I was watching a bundle of cpu, motherboard and memory go on ebay for over 320GBP.

I then saw some Advent (Curry's own brand I believe) complete systems going for around 450GBP which were i7 2600, 8GB memory, 2GB WD hard drive, ATI 6770 and all the other general stuff. So for just over 100 more you get an actual PC. Buck for buck the entire PC works out cheaper. OK, the motherboard is one of cheaper ones; but with i7 2600 still costing 224GBP in shops...

One idea you may want to follow (and something I am testing having got one of these PC's) and my idea (that is if I don't like the configuration of the system; i.e. the case look) is to strip out the processor, motherboard and memory and replace with parts I want to upgrade from; in my case the i7 920. Then resell the system with a smaller loss. So my aim for example is to make 320-340 back meaning I will have upgraded for around 110GBP.

Now; at a later date I may want to upgrade the motherboard - but this still will mean I paid 110 for processor and memory.. Make sense? Certainly considering that with motherboard it would still be below 200 and not over 320. Could even swap out 2Gb hard drive for a 500Gb got spare - even more financial sense.

Now; I may get back later and think "I like the design of this system" and so swap out the 6770 and put in my 6950 and sell on other system. But; either way to me this seems like the cheapest way to upgrade.

I'll let you guys know in a few weeks if this plan works out..   Anyone want to buy a i7 920 gaming system with 12Gb of ram and 6770   ;-)