Actually, your 550 probably has the most engine performance of all those you listed, unless you want to take an RD, port the cylinders, put TZ reed cages, big carbs and chambers on it.
It all really depends on your budget. I'd say look for a 90's Honda 750 Nighthawk. I see them for about $1500 around here, and they are light years better that your old bike.
And probably faster than that Thruxton or Sport Classic.
INCOMING!!!! TAKE COVER!!!!!
