At the risk of sounding dull and boring, won't you be on a restricted power output as some of your early posts you were riding a 125 and hadn't passed your test yet? If you have, well done, sorry I missed it!
Back to the point tho, from what you're asking for it sounds like you're a bit nervous of the power available on a supersports 600, hence you want one with sensible road manners, i know they don't look as cool ( depending on your opinion mind) as nakeds or sports commuters, but I really think you might want to seriously consider one. Any sports orientated 600 ( or even a good 400) is going to be a lot quicker on acceleration, mid range and top end than the 125 you've been used to. You say you don't like the riding position of the SV650, what about the fully faired ' sport' option, thats got the lower handle bar position similar to a supersports, but still with a very managable power spread.
Once you've spent a year or so on a more managable bike then you can trade in and step up to a more powerful supersports with confidence and hopefully more knowledge of what you really want from a bike, not what you think you want from magazines and far too many conflicting personal opinions.
Thats just my humble opinion, feel free to ignore it or take the piss whichever you feel it merits

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