Hi!
very interesting thread!
I have never been an a/c owner nor did I fly many different a/c.
Hope you guys don't mind I make a few comments.
- As flyingfemme said, if you think about making a gradual step up, don't buy something "cheap" now to buy something else in 2 years time. I'd suggest renting for 1-2 years until your budget and your desired a/c match.
- TB20 is really nice in many aspects (also TB200 and TB9).
- I loved the DA40 but I'm not sure they will do 600NM on max payload.
- Maybe some of the Cirrus can do the job.
About the last 2 options... not really inside your budget but you could consider renting. Probably if you can book ahead of time you can take them for a trip. If after a couple of trips you change your mind... the a/c is not yours so you can go on and rent another kind of airplane.
That's if you are not really adamant about purchasing and don't mind renting.
Then you have the added advantage of glass cockpit (I really love it!).
And if you can rent, the Bonanza (I only flew the 33) isn't a bad choice neither.
I'd not consider twins as an option mainly because of price and ease/complexity of flight.
The arrow II/III ... I'm sorry but I hate that plane. I think it might be a nice trainer but not a/c for touring and not sure about payload and range (although I never flew the turbo-arrow or the arrow V to be honest).
Just one final note about the range... 600NM can be kinda tight for most typical light SE a/c so maybe you may want to consider the idea of a quick fuel stop and besides stretch your legs etc... or even use the opportunity to stay overnight in a nice new place.
+4hrs of flight in a row can be tiring. Consider autopilot also!
Cheers / Pablo