Do I really need a sub?

I just installed 2 Alpine 6" x 9" 3-Way Speaker (Model: APN SPS690A). Vast improvement. No idea what kind of door speakers I have. The deck is a Blaupunkt Houston DM189, 188WATT CD player. I'm pretty sure I need an amp now, but am low budget and just a cruisin' around town listener. Do like some bass in my music selections but am getting distortion. What do you suggest? I only see posts on systems including subs. Would tweeters add anything alone or only w/ subs? I'm looking on eBAY too. Thanks!

you can't get deep, low bass without at LEAST a pair of 8's in a box, powered by an external amp

well uh, tweeters do the highs, not lows, so adding a pair of tweets won't help your bass at all. If you just want a little good bass then I would suggest getting a single 10" woofer and an amp. You don't need much to pick up where your other speakers drop off. Just 150rms to maybe a jl 10w3 would probably be plenty, but that might be out of your budget (2-300 depending on what you get and where)