Car audio instilation

Im kinda new to the car audio seen and dont know much about it but the basics so if you could explain something to me that would be great.  Can you explain the differance between, spl, and sq, to me???    and what are the best kind of subs for both thump and music??  

I currently have a 88 ford tempo that i have made some modifications on.

I have a 60watt road gear head unit and it is hooked up to 2 4 inch factory speakers in the front doors, and a 600 watt jensen amp hooked up to a pair of  10"boss american subs, i removed the rear 6x9s and replaced them with the 2 10" subs and it hits pretty good but i still want more thump and do not have a whole lot of money to throw into it!!!!!!!!!!!!!!!!    any suggestions?????????????????  SUBS?  AMPS?  WIREING? BRANDS? ALTERNATORS?  Anything?????????

Thanks for all your help

SQ is sould quality...I think that is self explanatory...

SPL is Sound Pressure Level...basically, how much cabin presure you can create in your car...

the difference is SQ is for people who want really clean sound and are willing to sacrifice some volume...typically people who really appreciate music...SPL is for people who are opposite...they will sacrifice quality of sound for volume, and they like it loud...

as far as your gear is concerned, I would save up some money before investing any more and wait until you can afford some good quality gear...neither SQ or SPL is cheap, and its debatable which costs more, but the bottom line is they both cost, especially if you want to be competitive...

SPL = sound pressure level. measure in dB, I guess it it's for loudness.

SQ = sound quality. the flatest frequency response subs/speakers would help the SQ.

These 2 subjects can get a lil complicated.

You get what you pay for. As for me..i really like JL Audio Subs and amps. especially those W7. as for speakers, i like MB quart.  These high end stuffs are expensive but you can get for less at certain location

thanks a lot for the info i just have one more question are the boss american subs any good as far as subs go??? i have 2 10" ones i like them quite a  bit and i got them in a sealed box for 35$ really couldnt go wrong but are they worth much???    i saw one 8" at an audio store in a similar box for 179$       did i get a good deal? and are they worth much for resale???

Thanks!!!!!!

THe Boss line of equipment is not exactly high end. The person trying to sell the 8" in a box for 179 is either crazy or greedy !! Here is a link to some BOSS subwoofers taht you can get for $ 25.00 ( x 2 sets of subs ):

http://search.ebay.com/search/search.dll?cgiurl=http%3A%2F%2F/.com%2Fws%2F&krd=1&from=R8&MfcISAPICommand=GetResult&ht=1&SortProperty=MetaEndSort&query=BOSS+Subwoofers