[Unlicensed Dremel]

OK, after some thought, I have a few for you which are sub-$600 pre-shipping:

Vortex Viper 4-16x44: http://swfa.com/Vortex-4-16x44-Viper...pe-P48287.aspx

Meopta MeoPro 4-12x50: http://swfa.com/Meopta-4-12x50-MeoPr...pe-P53877.aspx

Sightron S2 6-24x42: http://swfa.com/Sightron-6-24x42-SII...pe-P40519.aspx

Bushnell Elite Tactical 5-15x40mm: http://swfa.com/Bushnell-5-15x40-Eli...pe-P48272.aspx

Or, you could cut your budget in half and get a really good fixed power one like these, as long as you know you'll only be shooting at beyond 50 yards:

SWFA SS 16x42: http://swfa.com/SWFA-SS-16x42-Tactic...pe-P53715.aspx

SWFA SS 20x42: http://swfa.com/SWFA-SS-20x42-Tactic...pe-P53716.aspx

I have that last one and it's a helluva scope for the money. It's what's on my dedicated long-range varminter (analagous to your .204).

I'm thinking a Leupold VX3 4.5x14AO with duplex reticle.

Well that's good too - can't go wrong there.

Also, this one right here is half your budget due to being on clearance/closeout - very good choice:

Nikon Monarch 4-16x42: http://swfa.com/Nikon-Monarch-Riflescopes-C10194.aspx

I also cannot disagree with the Burris FF2 6-20x50 advice. Have a few Burrises and they'll all good. http://swfa.com/Burris-65-20x50-Full...pe-P53360.aspx
It will be *slightly* less quality than the other ones I mention, but still quite good.