Replacing my tweeters a good idea?

Sean, you are partially correct about what happens when a resistor is inserted into the speaker circuit. Output is lowered, tonal characteristics are changed. THAT IS THE POINT!!! Crossover frequency is left UNAFFECTED by resistors. Resistors merely attenuate the output. Here we want to tame a bright speaker. MANY, if not most speaker companies wire a 1 to 3 ohm speaker in series with the tweeter, on purpose. They want the speaker to be 3 db down at 15K. Why? Because most people complain the same speaker without that resistor is too bright. Crossover frequency IS determined by capacitors AND inductors. A capacitor in series limits a lower frequency being passed to a driver. And inductor in series limits a higher frequency being passed to a driver. A first order crossover has a capacitor on the positive side on the tweeter leg, and an inductor on the positive side of the woofer leg. If you had a midrange, it would have both a capacitor and an inductor in series(again, on the positive side) with that driver. Rolloff would be 6 db/octave, depending on the component values used. Adding an inductor in parallel to the tweeter, and a capacitor in parallel to the woofer(and both in parallel to the midrange) is a second order crossover(12 db/octave), and so on. Alternating these components in series and in parallel(maybe confusing, but no need to explain in detail here) takes us up to 4th order(normally). Resistors don't factor into this crossover equation AT ALL. Their purpose. To attenuate drivers. Say a tweeter with 91 db/2.83 V sensitivity is used in a speaker with an 89 db/2.83 V sensitive woofer. The tweeter needs to be quieted down a bit(we can't increase the woofer output), for the speaker to be balanced(I still listen before inserting the resistor - just to get a baseline feel). We may also need other things in the circuit(won't discuss them here), but they come later.

Audiopath..... you think I should try your stuff first? I am not sure about how to do room treatments, how do i treat the first and upper corner reflections?

also, the freq response is quoted as going to very high, like 35Khz or 45Khz, i forget... is it worth me using a high pass to cut it off at 20khz??

Trelja...I couldn't have said it better. Bryhifi...I spent two grand on power tools, bought 3 or 4 20 foot sections of PVC water pipe, and built a pretty cool cylindrical 3-way using SEAS 5 mid and 0.75 plastic dome, with Peerless 8 down-firing woofer. I had built a similar cylindrical speaker as a kid using 3 foot clay sewer pipes, mounting a coaxial Jensen or Utah (remember them?) driver upward-firing into a plaster-filled kitchen funnel for 360 dispersion. What a hoot! So I decided to revisit that idea with modern materials. Well, no-one seemed excited about a cylindrical shape, so I never built the second side. Sound was pretty good, although woofer/mid crossover was problematic. Got good at voicing crossovers, and noticed that I could hear 1/3 dB changes over 1.5 octaves in the upper crossover region. After seeing that raw driver sensitivity tolerances are typically +/- 5-10 times that level I quickly realized that it would be impossible to make speaker systems consistently without customizing each crossover, or spending a fortune to get tight-tolerance drivers. I built with others 20 pair of a nice 6.5/1 two-way a few years back that ALMOST got into production as a reinforcement system for a digital piano mnaufacturer. A local high-end dealer liked them A LOT, but we couldn't get the cabinet maker to take a repeat order at a reasonable price. Voicing a matched-pair of speakers is a labor of love, and I have great appreciation for those who do it well. I preferred these two-ways to many commercial designs for a long time, but after I heard what Bruno Pelchat et al at Verity Audio accomplished with their Parsifal Encores, in my living room, my jaw dropped! Had to have 'em! So I'm done...for now. (PS. Want a good deal on Seas 5" 'bullet' dustcap, or those tweeters? How about the Peerless CC line 8"? A nice router...or maybe a belt-sander? Oh well, it was fun. It's all about the process, anyway, right?) Shabbado...you mean "low-pass", and no, that's NOT what you want to do. Room treatment, upstream components, maybe 1-2 ohms on the tweeter: try 'em all, and have fun!

As has been mentioned your speaker system is the sum of it'parts.The drivers,box and crossover values were designed to work as a unit.I contemplated and did exactly what your thinking of doing.I had an average pair of small monitors that became test subjects.I disected the little guys and in the process with alot of other research learned a great deal about what constitutes a good sounding speaker.Trying to replace your tweeters involves alot more than just buying better ones.First off even if you had the specs for your existing pair don't forget that the new ones would not only have to match electrically but physically as well.Finding replacements with the same mounting flange diameter,bolt pattern ect. is the real challenge.If your determined to improve your speakers I'd go with the earlier suggestion of installing better crossover parts and again thats only if you can get a schematic with the exact values of the existing crossover parts.I have had excellent results with this approach.Generally you'll find that the major difference between an average speaker and a great one is the quality of the coils,caps and resistors.