Don't pay those gigantic premiums for a gaming laptop. You don't need the insane GPU those monsters house.
I've used workstations running dual Xeons, a desktop running intel quadcore and now a laptop running C2D P8600 and from my limited run with digital software it seems like the problem lies in the memory. You'd want at least 4GB worth of RAM followed by a decently speedy CPU, I don't think it's necessary to grab those i7 machines as I'm finding even the older Core 2 Duo in my T5010 is handling Photoshop without lag.
If anything, use my config as baseline, anything equivilent or better will be able to run Photoshop well.
Processor: Core 2 Duo P8600 @ 2.4Ghz
RAM: 2x 2GB DDR3 Dual Channel @ 532 Mhz
System: Windows 7 x64
"Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it." - Bohr