Would a new deck be better?

I went to a local car audio shop and asked about a EQ and he said what kinda deck you have and I said Sony CDX-mp40 and he told me buy a new deck and your system will be twice as loud I garantee..
Is he right. He said buy one with 4 volt pre outputs.
I wanna spend 400 CDN what do you guys recomend

 I don't know about twice as loud...  are you running amps to all your speakers or just running them off the deck? 

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You'd better get me out of this lord... or else you'll have me to deal with. -- Hunter S. Thompson "F.A.L.I.L.V."

If you switch to a deck with high volt preouts it will help, but you could also just buy a eq/ preamp that boost the signal to like 8 volts and its gonna do a better job. If you are happy with your deck than just buy the eq/preamp.

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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

I kinda want a diif deck im running my speakers off it but he said my subs will be louder

If you want good control of your subs right from your deck, I always recommend any alpine with the bass engine plus or bass engine pro. I'm not sure how much they run in Canada, but there should be one in your price range with 4 volt pre-out to the subs, 50 or 60 W x 4 (23.5 or 27.5 Wx4 RMS, respectively), and a bass engine plus. Otherwise, it's just a matter of brand preferrence. You should be able to find similar features on many brands.

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You'd better get me out of this lord... or else you'll have me to deal with. -- Hunter S. Thompson "F.A.L.I.L.V."

OK I have a big car stereo problem though just so you no; I always want more. I have a PPI 2150 amp 600rms @4 ohms . I had three type s 12s. they guy there said he use to sell these amps and it will run 2.67 ohms.
Should I just try the three out and buy a deck later since this amp already pushes these subs like crazy on half gain???????
The deck will basically be just to pound the subs better.