The DSLR-A100 was from around 2006 so it was the initial DSLR that was created by Sony and looking at it, the more that was researched and developed, features and specifications got better.
Then in 2007, the A700 was launched and was a beast of a performer and upgrades such as motor speed was introduced which was then implemented (or closely) with other models like the A200 which came out a year later.
More likely than not, it would have been a massive overhaul on the specs and abilities of the bodies since there is a 3 year gap (approx) between the A100 and A200. As much as firmware updates can help to improve certain things, I don't think any new or customer firmwares could improve focus speed in the long wrong.
I would honestly recommend considering upgrading to a newer body if speed is a factor since they have really improved in that area.
