Test ride both the GS and GSA to see which one you prefer - they do feel very different....
Options - go for ABS and heated grips as a minimum -otherwise difficult when it gets to resale time....
The rest is down to personal preference but for that money I would want luguage included in the package.....
ESA - some love it but personally I prefer to spend the money saved to go towards some proper supsension - Wilbers etc.....
Traction control on the GS's is so crude I would not bother.
Spot on
The GS feels quite sporty and chuckable with better feedback than the GSA, but the GSA feels a shade comfier and has a HUGE tank range - ride both and see what you prefer.
The GS Traction Control is very crude and cuts in too easily IMO often stopping hard acceleration even on goo dry roads, it also cuts in very heavy handedly (like someone has turned off the ignition) I am not sure this sudden cut-out would always be a help in a sticky situation. But the Dynamic pack also adds tyre pressure monitors and ABS so worth having.
Heated Grips are great to have, and I agree that a GS without them is likely to be unpoular just because 99% have them fitted so a potential buyer has lots of similar choice with them - a comfort pack provides the grips and the onboard computer and most bikes have this (or the premium pack which also includes them - but also has electronic suspension)
So look for Comfort pack as a minimum, Comfort + Dynamic will give ABS (and the slightly less useful TC) on top of the Comfort pack.
I prefer to buy top quality suspension, although can see how handy electronic suspension is the problem with the BMW setup is you can't tailor it, so if you are not the same weight as their "average" rider, with a pillion the same as their "average" pillion and carry the same weight as their "average" load then the settings will not be spot on.
The other problem is OEM suspension is always built to a proce, yet costs a fortune when it goes wrong, I am guessing replacing the ESA shocks when they are knackered at 10k / 20k or whatever will be expensive, my Wilburs work much better over a wider range and will last for years and can be fully rebuilt for far less than a new unit, and serviced every few years for about £200 to keep them tip-top.
2008 / 2009 are MU models - more pokey than earlier ones, but not quite as powerful and smooth as 2010 onwards, I am guessing your budget should get you a fully loaded 2009 easily, although you may prefer to get a slightly lower spec 2010 for the better engine.