These aren't too bad. A couple of my students have had these and they are pretty good-they may need some fret dressing and will certainly need new strings.
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I might also see about getting a used Ibanez SR506. There are some good used deals to be had on CL or Ebay from time to time.
New, this Ibanez SR256 looks like a pretty good deal, but I haven't played one:
http://www.musiciansfriend.com/bass/ibanez-sr256-6-string-bass-guitar
Finally, at the top of your range would be a used Carvin LB76 if you can find them.
http://www.ebay.com/itm/Carvin-LB76...A-/121124995321?pt=Guitar&hash=item1c339cc0f9
Oops, sorry, didn't see that about not wanting used. Besides the Rondo and the SR256 try this one:
http://www.musiciansfriend.com/bass/esp-ltd-b-206sm-6-string-bass
I agree with all these options. I own almost all of them.
SX-6 is dirt cheap Fender clone 6 string. EXCELLENT after a few mods like strings, shielding, maybe some fret filing. The Brice basses are also great basses too. They are active modern soapbar kind of basses. Usually owners talk about swapping electronics but loving the rest.
I've got a Ibby SR506. Got it used for $250. Deal. It does it all. Really nice bass. I also like my GSR206 which I bought first for about $200 used. Has a couple of construction issues (volume not even over all strings) but killer tone and playability. As soon as I had it in my hands I knew I had to own it! Even new these are not huge expense.
The SR256 seems to me like a version of my sr206 with the problems fixed. Looks like a great buy, but I've also not had a chance to play one yet.
Carvin's can be great deals used, but you don't want used and new is over your limit.
And lastly I own an ESP LTD B-206SM. An Absolutely killer sounding, playing and looking bass for not too much coin (a bit over $400)
It's really up to you. Here you have the three classic bass sounds. The SX-6 is the classic Fender jazz in a 6er. The Ibanez SRs are ALSO classics in their own way but nothing like Fenders. Soapbar fat tone, light weight, thin necks, and easy playing. And lastly there is the ESP LTD which is a looker and the very essence of what is called a "modern"
bass. Bright tone. Excellent electronics. Killer neck. And very modern coffee table wood look.
Believe me a person could fall in love with ANY ONE of these 6er basses for just what they are even though they are all quite different. That choice is up to you.