For my money I would go with ESP F series. It comes in a 4 and 5 string (F-404 and F-405). These are around $700 but can be negotiated down to $650. They also have the less expensive F-254 and F-255, which look the same, have the same pickups, but different hardware and tuners.
For the Money you can't beat the ESP models of which there are many many under $600.00 price range
I saw somewhere somebody in this thread typed ESP's were generic sounding....nothing could be further from the truth...but opinions are like backsides everybody has one and they all think theirs smell better than the next guys....
The tone on my F series ESP is absolutely amazing it blew the Warwick Vampyre i tried the same day right out of the store
Just a few Metal Heads (Bass) that play ESP
Dave Pybuss of Cradle of Filth
Henkka Blacksmith from Children of Bodom
Orion from Behemoth
Mike Ruehle from Full Blown Chaos
Fred Leclerca from Dragon Force
Mick Deth from Eighteen Visions
Aaron Patrick from Bury your Dead
Bobby Burns from Soulfly
Danny Horboychuk of Dry Kill logic
Steve Unger Metal Church
Steve Digiorgio of Testament
Beefcake the Mighty of Gwar
Pig Benis of Mushroomhead
Laz Pina of Il Nino
Tom Araya of Slayer
Brian Redman of Three inches of Blood
Scott Crochet of Soilent Green
John Miller of Devil Driver
Just to name a few off the top of my head...
as i type this
Musicians friend has 73 basses currently listed in the under 600.00 dollar range
best advice is go out to your local store a play what catches your eye and feels good in your hand...as your playing and skill advances then you can always trade up....
Play what you like and like what you play
Later...