I'd strongly recommend just getting the 8x42 SLC-HD. I'm sure you could probably do a straight up swap on certain forums, as 10x is valued more than 8x in some communities (namely: hunters). The 8.5x Swarovision is a great pair of optics, but I don't think the 8x42 SLC HD loses much to them (the SLC HD is bright, sharp, and fairly color neutral). Also to consider, the ergonomics and focus speed are quite different with the SV and may not suit you as well as the SLC-HD you've been accustomed with. I've owned the 8x42 SLC HD, 10x42 EL (non-SV), and 8x32 SV AND spent tons of field time with a borrowed 8.5x42 SV, so I am familiar with all models mentioned. The biggest advantage of the Swarovision over the SLC-HD is the near distortion free image edge to edge, but I personally found the SV to have slightly more chromatic aberration and to be more prone to glare than the SLC-HD; the SV may be slightly more color neutral, but that's nitpicking to the extreme as I'd consider both quite neutral, moreso than any other alpha I've owned or used.
I'm of the opinion that you don't necessarily need an 8x and a 10x - a 10x really doesn't provide that much more as you have to factor in hand shake and a dimmer image. I'd rather have an 8x and a small scope (ED 50 or similar) or a pair of 12-15x binos. 10x has been occasionally useful on waterfowl surveys, but typically if I can't identify a bird with an 8x, the 10x isn't going to give me enough detail to do so either and I have to grab the scope, anyways.
Justin