12-15K is WAAAY more than enough. Stay true to your brand and get a Honda. I'm familiar with every one of them as far as dragracing goes. Go with a Blackbird. The 900RR's will cost a ton to go fast and you'll spend a fortune repairing #3 rod journals on cranks. Plus they are harder to launch as is the 929's, 954's and the 100RR's. Buy one already set up for dragracing. Airshifter, electronics, swingarms, etc. will cost small fortune. You can get one in the 6K range pretty easily. Just last year there was one running high 8's in 1/4 for 6500. Blackbirds are very easy to launch, parts are pretty cheap(comparatively speaking), and are dependable. I can find you one if you'd like. Been doing this since 97 so I've made a few connections along the way. Get a drag only bird for around 6-7K. I have a 6x10 enclosed trailer which is plenty for 1 bike operation. You can get used ones in 2500 range all day long. That leaves you PLENTY to buy a few spare parts and such.
XX motor in a 900 frame...Come get some.