Sir, I'd advise you to find decent, informed shop owners and stick with them. Members from Karachi can help you with finding some.
For finding items as rare as the one you originally set out to find (the Infinity), get them sourced from reliable members here (I believe you've been here a while, you should know by now). And keep the market rounds for entertainment purposes only LOL, they yield a few good laughs but usually nothing more. =)
As per your query regarding the Pioneer and JVC subs, they're entry level ones. I have personally used the JVC one, was good for the initial dazz-dazz phase in a traditional vented box, after a while I got tired of it. Upgraded to a JBL GTO1214, one of the best decisions I ever made.
You set out to find an brilliant SQ sub, keep at it. =P The replacements @bad_cheetah suggested are brilliant subs in the price range. Look for, and test them. =)