Looking for an upgrade over my current one

Ok so here is my current laptop

HP DV7-4071nr
i7 720 1.6GHz
ATI 5650 (550/800 stock and its overclocked to 700/1000 on A/C power)
4GB DDR3 1333
500GB 7200rpm
DVDRW
17.3" screen
7.99lbs with 9cell 93whr battery
only paid $578 after $100 rebate

So what i like about that is that its pretty fast yet pretty thin for its specs, fairly light for its specs and gets good battery life when not gaming at around 3hrs (i understand battery life while gamming sucks)

But i want something with a bit faster GPU like an ati 5850 or so but i want something thats physically similar, ie i dont want a 17lb clevo.
How much faster will the 5850 be over my overclocked 5650?

Other things hardware wise, if the computer is a slot loading drive then it has to be a blu-ray drive (can be just a reader) as i dont want to deal with swapping out a slot loading drive bleh.
Dual drive bays is a must, i want to have a SSD as the boot and a larger mechanical drive as a secondary

Was thinking the 17" HP ENVY fit the bill but wanted some more opinions.

Price can be up to $2500

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