Speakers question

[dimme]

I have one set of speakers, don't know their effect but they sure roar, that's for sure. It's a 3-way system containing one tweeter, one midrange speaker and one 12" bass speaker that goes down to 30Hz. Now since these speakers are old I have thought about upgrading the bass speakers.
I have had my eyes on a 12" speaker with a 7.5 lbs magnet 500W peak and 200W RMS power with 4ohm impedance. It's actually for a car but it can be mounted in home speakers, too right?

Now I don't know what impedance my current bass speakers have, if they are 8ohms, what difference will the 4ohm speaker make? I'm not looking for any hot shot high end bass speaker like cerwin vega or infinity kappa, just a good bass speaker element for some money (stress the some, I'm a student dammit).

Remember I'm a n00b in this. Give me as MUCH info as you can about it
I don't want to end up with a ruined speakers in my hands

EDIT, the speaker box is pretty big, measured it and it's a 94 litre (3.36 cubic feet I think, NOT SURE) box, yes it's big.

Thanks

 

[Gonzo]

the lower the ohms, the less the impedence. which roughly translates to less clutter in the way. You CANNOT & MUST NOT mix impedence. Find out what the current ones are & stick with that or replace everything.

 

[dimme]

Ok, thanks for the info.
I've seen different woofers but they all weigh differently, does the weight of the magnet have an effect on the sound of the woofer? have seen speakers with 116oz magnet that costs $40 and I have seen speakers with a 70oz magnet that costs $100. All 12" woofers.

I have only found ONE 8ohm speaker in my price range. What do you think of it?

Impedance: 8ohms
Sensitivity: 92db
240W max 120W RMS
30oz magnet
Vas 138 liter. Fs 27Hz. Qts 1,16. BL 9,2.

 

[Gonzo]

$50. or $1000. irrelevent. how does it sound? that is the only key that matters. I love Boston Acoustic speakers, but they sound awful for the type of music I like. Numbers are for show only. If they sound good, buy 'em.

 

[dimme]

I just opened my speakers and the current 12" woofers in there are "GAMMA HIFI BK 3013 A" 8ohm speakers.

The 4ohm speakers I've seen are perfect for my use and they don't cost much. Would the sound difference be big with 4 ohms?

edit: The amplifier I'm using is a Marantz amplifier, pretty big with lots of power. Don't know if it runs 4ohm though.

 

[Kruz]

the lower ohm speakers will give you more power out of your amp.. *less resistance* BUT !!! the amp can (and will) overheat if it was not designed to handle the extra load\heat