Anywhere from $150-400 new, each. What exactly are you trying to accomplish here? More dynamic sound but with good accurate reproduction and proper imaging? Or just trying to be heard from a half mile away? Really hard to give any suggestions without knowing your actual goals. Too many people equate pro audio with "who cares how it sounds as long as it's loud!" (and many of the users require only this level performance out of their own systems using these speakers), so when someone asks for recommendations on high sensitivity drivers the suggestions pay little attention to the actual quality of the sound produced or goals for the system. Most of those "loud" pro audio car setups don't follow the best acoustic practices either. The reality however is that there are lower-average quality products that have lower-average performance and higher quality products that are very well behaved in terms of distortion, linearity and response. Knowing your goal will determine which product range fits your needs. Also, knowing your goals as far as imaging will help provide a realistic expectation as speaker placement and as a result, size constraints. I will say that you are not going to find a high sensitivity 3" or 4" driver. Sensitivity is partially a function of cone area, and as cone area goes down and motor size decreases, you begin to limit the driver's ability to maintain a high sensitivity. So matching a low sensitivity 3" full range driver with a high sensitivity midbass and midrange is going to require you reduce the level of the midbass and midrange to properly level-match the drivers......which sort of defeats the purpose (unless you are purchasing the high sensitivity driver for it's other traits, such as distortion performance. But that doesn't sound like your objective). Also, most super-tweeters or bullet tweeters need highpassed in the 3khz - 5khz range. A 6" driver is going to begin beaming well below that point as well as probably run into some potential issues with things like cone breakup modes/etc. Now, not all beaming is bad as it can serve as pattern control, but it's also not always good or useful and can create another layer of complications to the installation/tuning if good sound and imaging is your goal. Horns in generally are not newb-friendly. That's not a knock at you as I have no idea of your abilities, but if your tuning skills are on the newer end of the spectrum expect to spend considerable time tuning the system before it sounds (atleast until you get that MS-8 listed in your sig which will take care of most of the hard work for you). However, for other reasons such as better pattern control and horn loading as well as available bandwidth (and overall performance in general) they are a much better option than bullet tweeters. So, after a bit of rambling......what exactly are you trying to accomplish?