Will this system work well?
 

db 6501 4ohm in the doors and tweeter locations.Polk Audio db6501 6-1/2" component speaker system — also fit 6-3/4" openings - Reviews at Crutchfield.com

a JL audio 500/3 amp XD500/3 - Car Audio - Amplifiers - XD - JL Audio

and a JL 10w3 2 ohm in the Magic CAS corner box in back 10W3v3-2 - Car Audio - Subwoofer Drivers - W3v3 - JL Audio

The JL 500/3 should put out:

75w x 2 @ 4ohms to the db6501s and
300w x 1 @ 2 ohm to the 10w3 sub

does this all look alright?

I currently have the db6501s running off a 75x2 Polk amp, which I plan to sell. Trying to avoid adding another amp, by getting the 3 chanel JL amp.

Yes that would work, you might even want to upgrade the speakers to the MM series for better sound.

Yeah, I was considering upgrading to MMs once I got the sub taken care of. Are they that much better than the DBs?

Also, do the MMs require a mounting bracket or spacer to fit in the doors?

Check the reviews here: Polk Audio MM6501 6-3/4" (Oversized 6-1/2") Mobile Monitor (MM) Many mention how much better they are over the db's. I'm doing the same thing you are.....trying to get the best system together. Good luck to you and let us know how you like it when it's complete.

that is a good match...
May want to check out the Hertz Audio line for speakers... they will cost a little more but will get you better results...

Unless you call me then thay won't cost so much... :tup:
I can also get members of the370z a great deal on JL amps...

Sent you a PM.

I ran the MMs, no rears and 2 8" W1s on a JL 500/3. Got the job done, but I for one was bothered by no rear fill. A member was selling his Wicked Cas Spare tire box with the 13" jl and a JL 700/5. Ended up swapping that in and installing polks in the rear too. Finally satisified with it for now. My last stereo was Polk MMs front/rear with a JL w6 with a JL 500/1v2, JL 300/4v2. Needless to say, I personally found that The 700/5 with the rear fill did the trick for me.