If you like the bike I would suggest a higher screen, risers for handles, adjustable pegs, sculpted seat. The seat is the most expensive but chances are if you sell the bike you will get your money back on a decent gel seat as we're all getting old and creaky and for older riders it's something that might say 'buy me' over a stock bike.
Other than what's been suggested, I can only suggest a ZZR1400 or Thunderace (have/had both). The ZZR14 is a rocket in a straight line but great all rounder. Handles at least as good as the Ace and that was easy to flick about (that said I am on the larger side). The Ace is cheap, but most need an oil top up after 1000 miles or so. Pack a small bottle of oil under the cavernous seat.
The zzr14 has enough storage space under the seat for a couple of postage stamps, so not really practical without boxes on. Everyone wants the 12 plate on so pre 12 you get a lot of bike for your cash, 200+ mile range, hyperspeed or pussycat round town, loads of them to choose from etc.