Something with an i7 if you plan to record/stream a lot with a 970m would be more than sufficient, but those are around $1,500 on newegg... Could probably get something a bit closer to the $1,000 range if you are sure you won't play anything other than RS
Unslain Bosses - Clan
Your best bet would be to make a thread/post on Reddit, ask people what mobile gpus they are playing on and how the performance is on NXT (granted, it's a beta, less optimised etc), then find a laptop with that + an i5, or maybe an i7 if you can afford it. Job done!
Unslain Bosses - Clan