I have spent all kinds of money with Holeshot on my Bandito. I can't say enough good things about Dale Walker. Pretty much all the major upgrades I have done to mine have been through them. Looks like they have a lot of good stuff for your 1250 too.
For mine, the best dollar value upgrades were the Stage 2 jet kit (for you I would go TFI tuning box, O2 bypass, and K&N filter HUGE DIFFERENCE!!!!), full exhaust, timing advancer, Race Tech fork springs, Race Tech Gold valves (had RT do all the work too), and Progressive Suspension rear shock and spring. The stock suspension SUCKS! Those upgrades made it an ENTIRELY different animal. It is sooooo much better! It's now not all that far away from my R6 in handling, and the ride is 10000000x better!
Oh, and just those few power upgrades made a gigantic difference. They are badly stifled from the factory and insanely lean. I know it's not nearly double the power, but it feels like there's twice as much power, it runs SO MUCH BETTER, warms up much faster, starts easier and faster. Great stuff! Getting the head ported, installing the big bore kit, and changing out the intake cam made a big difference too, but nowhere near what the first upgrades did especially in the rideability and fun department. I also dropped a tooth off the front sprocket too. Cruise RPM went up a little, not too bad, but there's so much more torque.