@DrSpan : If you have a KH80 and now want to build another near field monitor, I would suggest you choose 3-way mini monitor route. Even though the solution Kef coax + woofer is a great choice, overall the sound is not too far different from your KH80. After all tweeters of both speaker use waveguide, so directivity at treble is controlled but more narrow than 3-way monitor without waveguide.
Like you, I also plan to build a near-field monitor, but in small budget. I also want that it can translate to surround speaker in the future. After researching, my plan is using a BMR driver TEBM46 for midrange from 500 Hz to 3000 Hz and SB Acoustics SB26SCTN for treble. Their off-axis response is tracking each other nicely up to around 6kHz even at 60 degree off-axis.
For woofer, I uses SB17CAC since I have a pair lying around but you can use a long throw 6-7 inch driver like 18w/8434 or CA18RLY/CA18RNX for woofer. If you use subwoofer at 80 Hz, you can get away with sealed box. It is easier to design and has better group delay in bass compared to vented design.