The tweeteres poping are probably because they are being overdriven. I'd look to upgrade to something either more efficient, or can take more power. THere are some really good ones for under $25/pair at
http://www.partsexpress.com/pe/showprod.cfm?&DID=7&CATID=35&ObjectGroup_ID=51. I can recommend ones in particular if you'd like.
