I use my Sony Laptop on travels, there the connection in hotels is a more limitating factor than the machine itself.
Nowadays you can buy most laptops and get sufficient power for SL unless you want to tune up grafics to max or want to jump into a mass raid.
So just keep your eye on a dedicated Video Card (formerly NVidea was the choice, since ATIO had probs with SL or vv., but doubt its still the case) inside and not just an integrated chip on mainboard from Intel or similar. More than the standard RAM of 4 GB certainly won't hurt. SSD is nice and the future, just remember, that the writing cycles on a SSD are limited, so using the disk for your cache might lower lifespan significantly.
If you are unsure, go for laptops they announce as multimedia laptop or so, These have enough power for SL already, or, if you want to spend really much and have highest expectations, go for a gaming laptop, but honestly, they are too expensive and not really mobile with their battery seldom allowing longer worktimes than 1 hour.