I guess we should clarify, when you say new detector, do you mean brand new, or just new to you? Used adds to the choices, but for $500 many new detectors fit the description as something you might want.
You probably know you can get target ID, depth indicator & non-motion pinpoint for about $200 new in the Garrett Ace 250 or Fisher F2.
If the idea is to get something better than those, the Fisher F5 mentioned previously is probably a good choice. I had one, but replaced it with a used Fisher F70, which I got for under $500. I also got a Minelab X-Terra 70 used with 2 coils for under $500. Target ID, depth reading, non-motion pinpoint, + they are both lightweight & use 4 AA batteries with rechargeables being a good choice if you detect frequently.
I have terrible soil & only dig signals likely to be coins. Deepest with F5 was 4" and with Fisher F70 5"+. A Garrett Ace 250 got me 3 1/2" with ID lock.
Think the Tesoro DeLeon is under $500 new? (somewhere around there). White's has Prism V, but Prism 6T (599.95 new, but occasionally seen used) would be better.
The 6T offers backlight & ground tracking & faster response. 8 AA, under 3 lbs.
Teknetics offers the Delta 4000 for $399 & the Gamma 6000 for $499. You can read a good analysis of the Teknetics & Fisher newer models at non-commercial site
www.fisherf75.com
China offers a detector with visual ID, tone ID, depth reading & non-motion pinpoint under $150 (air test 10" on quarter).
Bounty Hunter offers Land Ranger & Time Ranger under $500.
Older detectors can offer good value for money, but tend to be heavy and may require many more batteries.
You can see professional reviews at
www.losttreasure.com and reviews by anyone at
http://metaldetectorreviews.net/ This site will make it clear the wide range of opinions on any model. Frustrating to see "one of the best' & "one of the worst" being said about the same detector. Some reviewers may have misadjusted something, but often which detector does best will vary with the soil.
If one detector was best for everyone, we'd all be using the same model. I guess a deciding factor might be what most call little things, that bother or please some people more than a little. Most will recommend whatever they use.
I realize I've rambled on & maybe just made it more confusing. I will try to help if you have more questions. Oh, then there are some high-tech detectors made overseas in all price ranges. Plus all the coil sizes, shapes & types.
A site with no mfr or dealer ads, but tech forum with engineers, field testers & long-time detectorists is here:
http://members5.boardhost.com/MetalDetecting/
HH all, George (MN)