I've done a bit of searching and I've noticed that 4kHz is pretty high for most comps on the market. In fact I haven't seen any numbers higher than that. I also noticed that the higher quality the comp, the lower the cross-over point.

 

... I wouldn't say a high price makes something good

also I would not say a crossover point is a good litmus test of quality.

Remember the goal of the manufacturer is to make the best looking and sounding product AT A PRICE POINT. A mid-bass that can easily reproduce HF takes a load off the tweet and a cheaper tweet can be used. So it is all about trade offs to get mid-bass whack and HF extension in a typical cone driver. Inexpensive plastic cones do the HF part well but give a hollow whack, while paper does the whack better than HF. My highest SQ score ever came when I had a blown right side midbass (8" Dynaudio) and I replaced it with a 5" vifa ($25) since I smoked the Dyn' the day before the competition.

 

So I'm thinking that a DIY replacement may be more work than I am able to do. So back to the original post
Comp options:
Flea-bay infinity comps
Local Kaption 6" comps from a dealer
Or something else that is local to the Niagara region (If anyboody is familiar with shops here in Niagara)

 

Have you checked with some of the dealers on here, many of them can sell you good equipment, authorized for good prices.