New Cartridge

I have a Rega RP 3 turntable with a Exact cartridge. Thinking of replacing it my budget is $600. What recommendations can you give me. I have the Rega phono preamp and speed control. My pre amp is a Rogue Metis and have a Carver 1.0t MK 2 Opt 2 amp. I have Source Technology 7211 speakers with 2 Source Technology sub’s. I listen to classic Rock and Blues. Thank for any input.
You have to study the basics about cartridge design first.

-Cantilever (conventional like aluminum or exotic like beryllium... etc)

-Stylus tip (nude or bonded, the most important is the stylus profile, you’d better ignore cartridges with conical or even elliptical tip)

-Cartridge compliance to match your tonearm (you can’t use low compliance on your arm, mid compliance is what you have to look for)

And with $600 stick to mid compliance MM or MI cartridges. Some of the best carts designed in the 80’s could be found with the best possible options, because new models at the same price does not have advanced cantilevers or best diamond profiles, in my opinion they are inferior (with some exceptions).

*If you need exact recommendation on some particular model send me PM

Do not buy MC cartridges, because you can not change the stylus yourself, you will pay crazy money for re-tipping process and some re-tippers will make your cartridge even worse than original using none original parts. A typical life span of the stylus is 600 hrs. 

Some decent MM cartridges can be used for 1200 hrs if the stylus profile is MicroLine or MicroRidge and you can swap styli by yourself in a 10 seconds (this option is ONLY for MM/MI cartridges, not for MC).  

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Forgot to mention really like to stick with a MM cartridge.

Good choice, you can also look for Moving Iron, Induced Magnet and even Moving Flux for use with MM phono stage. 

Dynavector 10x5 would be the obvious choice which is known to work great on that table.

Apparently Nagaoka carts also play well with a Rega and generally seem to be underrated the MP200 or 300 would be in that range.
I had the same TT with the Exact 2. Unless your stylus is worn out, I'm not sure you can gain a big improvement at your budget.

this cartridge output is too much (6-7mV), the diamond is fine (Vital), but the rest is nothing special, this cartridge can be easily upgraded within $600 for much better cartridge. I want to remind that Rega is not a cartridge manufacturer. 

Also i can't remember anyone said anything good about this rega cartridge on audiogon, almost any good MM cartridge discussed and compared to each other in MM thread for decades. 
Sumiko moonstone $300, sumiko amethyst $600. Look at Mike Fremers review of the Moonstone on analog planet....great review. A really nice budget mm is the shure m97xe, now discontinued....but it can be had at a price. I own one on an alternate Lenco turntable and it sounds fantastic. Quite honestly, if it were me I’d make the move toward a m/c cartridge...the Hana el ($475) or the audio technica AT F-7 ($289). Another is the Ortofon Quintet Blue ($524). To me they just sound better. I have a brand new sumiko blue point no 2 (high output moving coil) I could sell you. It will work on your mm phono stage with no step up required. 
If you can find a new old stock AudioTechnica AT-12SA cartridge you will be happy, it's a MM with a shibata diamond and can be found for around $200.00 - $250.00 I have been using this cartridge for over 30 years, just replacing the stylus, plus I have 2 brand new cartridges in waiting in case something happens.
I have the same table and arm and a Hana eh and wouldn’t recommend it for rock imo.  I am currently looking for a phono stage to match this Hana .. with my current set up , gain is an issue .. my present preamp is just a bit shy of the necessary input of 2mV.  Anyone with phono stage input would be appreciated.  
Actually, now that I think of it, I had an Ortofon MC3 Turbo for years. It’s quite excellent. Detailed, lively, and neutral. It doesn’t get much coverage anymore but it’s not expensive and sounds wonderful on all types of music.
 I am currently looking for a phono stage to match this Hana .. with my current set up , gain is an issue .. my present preamp is just a bit shy of the necessary input of 2mV.  Anyone with phono stage input would be appreciated.  

@drz771 Why not just add SUT for your phono stage ?

I agree that the Exact is nothing special on a Planar 3 or 6. The Moonstone is a bonded elliptical so despite MF’s praise it fails on Chakster’s criteria. The Sumiko Amethyst is the one to look at, or why not the Ortofon Bronze for less. Both would need to be shimmed. Buy the Acoustic Signature kit and tweak away!
I have the Ortofon Bronze for a few months. I'm very satisfied, big improvement over my Grado red II.
It's in your price range.