sooooo
To bring this back on track, CB500 should be good? 
Any of the 500cc twins are good - Kawasaki ER-5, Honda CB500 or Suzuki GS500. The Kawasaki is probably easiest to ride, and has the lowest seat (not so much of an issue for you), and will be cheapest. You have to keep clean, as the finish isn't that great. I used to frequently do 130m rund trip for work on my ER-5 - wouldn't want to go much further as when I arrived (65m) my arse was getting to the point of numbness. CB500 more comfortable imho, but more expensive, but everyone has different views of comfort.
Also, if you want a shade more power, the SV-650 V-twin is a good first 'big bike', very forgiving.
Beyond that, the Hornet and Fazer 600cc - this are in effect an unfaired, detuned versions of the respective 600cc sports bikes. No disrespect Tunnie, but you may want to wait a while before going to this level, based on my knowledge of your capabilities
