If you were to swap out the drivers in the KLH for new one's, you'd have to have a completely new crossover designed. This would effectively take your KLH and turn it into a KLH cabinet with WarMachine4444 "sound".
Attempting to design a crossover is no easy feat and something none of us would recommend you try (because, well, you'll fail) without quite a lot of research. You'd also need measuring equipment, as well as the knowledge needed to use it properly. I've been leaning about speaker engineering for almost a year now and I don't even want to "design" a notch filter. xD
You should take your KLH along and A/B them (make sure to match volume with pink noise) with the other speakers.
ScanSpeak is probably the most expensive on the list. They do make excellent drivers though.
DIY Speaker Components | Replacement Speakers | and Speaker kits from Meniscus Audio Group
a very very large risk..
Instead of paying this shop to design a speaker for you (with a set box no less...) why not do one of the options below, and buy a design that is proven and tested?
Not at all!! I wanted speakers that sound like the $22,000 Revel Salon 2 with a budget of only $2,000. I got VERY lucky. If you want the best bang for your buck, you can do one of two thing:
A. Buy the SM1 + Marantz SR6004 because it is a great design and i'm very confident you will be happy with this system for a long time to come.
B. Buy the Marantz SR6004 and buy a DIY flatpack. There are many good designs out there. GranteedEV and myself (as well as others) can help you choose one.
Both options include a new receiver because, well, you need one. Even if you did get a new crossover and some new drivers for the KLH, the odds of the receiver being able to handle the new speaker are slim. Likewise, it defeats the purpose of upgrading your speakers when your amp is THAT poor. (Wow, never thought I'd recommend a new amp before speakers.. :O)
I agree. My Philharmonic 2's are plain black and I am more than happy with them.
I don't mean to crush your hopes, but what good is giving advice if I can't at least make you a little sad?

xD
I don't blame you for wanting the most out of your money, but swapping out drivers is a good way to waste all of it...
If you think buying the M1 is risky without hearing it, just think of how risky it is to pay a store, with who knows what level of expertice, to design a completely new speaker from your existing one!

At least the M1 has been tried, tested, and designed by a competent designer.