Hi John,
Its what you feel comfortable with, DELL are a big no no! And so is PC world!!!
I bought a machine from CyberPower in 2008, it was a good machine but since then I've learned so much about PC's, I have upgraded everything in it barr the CPU.
£1600 will certainly buy you an excellent ready made PC, but almost everyone in the gaming world will tell you that its a better option to build your own. I just dont let myself get bogged down with fancy names and numbers of components etc!
It also depends on what you call 'future proof', me I say 4 years, some gamers on here are that keen and have so much money to waste they'll upgrade every 6-12 months! lol
If you don't want the hassle of building a machine then buy one form either:
Scan computers up here near me in Bolton: http://3xs.scan.co.uk/ShowSystem.asp?SystemID=1134 its £40 over your budget but will last for years!
Another great builder is Cude247
PC specialist aren't brilliant but OK for smaller budgets.