I met at a CES show in N.Y. years ago one of the heads of the factory from Proac. He said they used 'stock' Scan speak speakers off the shelf. He said what made their speakers special was all about the cabinet and the extremely beautiful book-matched veneers. So, unless you have excellent woodworking skills and a shop and a finishing booth with spray equipment you won't get the same results.
However, you CAN build your own speakers that sound every bit as good as good as factory built speakers. Danny Richie sells kits that are excellent quality. He is an expert crossover designer also. For fun I recently finished a kit from Swan that are incredibly good 3 way speaker kit. I made crossover changes and set them on 12" subwoofers. They are incredibly good with proper modification.
Whatever kit you choose the biggest challenge will be how to get them to look good. Everyone always tries to duplicate a factory veneer finish and they always look armature. Here is a method I use to produce beautiful looking speaker and takes minimal table saw skill. NO spray booth, stains or finishing and yields a beautiful high end look. The box is square. I glue a 1/4" rounded wood molding from Home Depot to the outside edge. This gives the speaker a nice rounded edge from the front. Fill and sand so it's a perfect smooth appearance. Then simply spray can a flat black finish to the face. This leaves the remaining sides of the cabinet unfinished. They sell all kinds of beautiful pre-finished veneer at Floor & Decor. I got some 'African Tiger' wood that was amazing. It matches the same 1/4" thickness and mates perfectly to the 1/4" molding. Carefully cut and fit each piece and glue it to the MDF cabinet. The only requirement is a thin sharp table saw blade to cut the 45 degree angles. The pre-finished flooring 'clicks' together for a perfect seem fit. After you cut and fit all the pieces you are done!! You end up with a professional finish that looks amazing. A flat black, rounded, front face that flows into a red and black African Tiger wood. This looks far BETTER than most square face,veneer speakers. BTW... the selection of colors of pre-finished wood flooring is HUGE and the finish is as good as it gets.
No painting my subwoofer cabinets either. They are finished in high gloss black granite. I have a tile wet saw and using urethane glue attached the granite to the mdf cabinet. This was not only beautiful but added mass and rigidity to the cabinet like nothing I've ever seen.
I am an experienced cabinet builder with over 50 years experience and I'm always unimpressed with DIY veneer cabinets. The staining and finishing is far more difficult than most people realize. The above method will yield a far better result, faster build time for less money.
You CAN definitely DIY an excellent pair of high end speakers. The 'Factory' doesn't have a magic wand to wave over their finished speakers. If done properly diy can outperform many factory speakers costing thousands more. Do the research and find out what makes a speaker box sound good (or ask Danny Riychie) Then finish it properly so it looks awesome.
Good luck!