Erin has the Dayton ND16 and I have a peerless, both available on parts-express.com. Given your experience I'll go on a limb and say you won't notice any difference between a good pair of inexpensive tweeters and a good pair of high dollar tweeters. There are quite a few tweeters that are under $30ea that will do the job just fine. Look at the site and see what will fit your application, i.e. some are really small and have little in the way of mounting provisions (like mine), while some are large and designed for 'home' use (big magnets, big mounting flange, etc.).
Another option to consider is a small wideband speaker. The Aura Whisper is a 2" speaker that costs 10-15 bucks (the occasionally run sales) and is a proven little speaker. Yes it is 8ohm. Yes it has low sensitivity. However, it has been used very successfully by several people including one back-to-back meca champion competitor. It is small enough that it could be mounted in the sail panel if you so chose. A similar sized option is the Tectonic Elements 2" speaker. Erin tested these a while back (review
here). An added benefit of a small wideband like those is your midbass driver options can open up. Meaning since you won't need to mate your 6" speaker up to a tweeter, you can focus on a 6" speaker that is better at midbass duties and not worry about the midrange performance. Dejo metioned Psyko's mustang, which you can see
here. I bring it up again because he had factory 8" speakers in his doors. If yours does as well then you have more options available to you. From 8" speakers (daytons, sb acoustics, etc.) to a beefy 6" like the Anarchy ($65 each online. Note is has a deep mounting depth so checking spacing would be a must) or a whole bunch of others.
So it is entirely possible to have under $250, maybe under $200 in your front speakers if you wanted to.
The Arura
The Tectonic