If it was me, I wouldn't waste the time trading from a Redeye to Redeye S/S. Unless you don't get killed with trade in value (that would happen to most people). The S/S doesn't appeal to me enough to trade in my 19" RE whatsoever! I wouldn't mind the demon brakes and suspension. However, the WB only option annoys me. Not everyone likes the WB, and the Demon 18" wheels are heavy. Every serious Demon racer ditches those wheels and crappy nittos. I'd rather swap out demon brakes and suspension, and mod my PCM than take the hit on a trade in. The WB option is a deal breaker for me, it kills the classic challenger lines. Now IF the S/S can be had like a Demon (1 seat no options), that would help it out a bit for the serious drag racer.
The WB RE Charger looks a lot better than the WB Challenger imo. Just my opinion of course, but the RE to RE S/S isn't a big enough difference. The only thing that would make me consider a trade in is a lighter platform at this point.