Personally, I like my White's and wouldn't trade my DFX for anything...except, maybe, a V3i - maybe. For coils, I'm a big SEF fan. Yes, they're foreign. And, yes, Kellyco is the only place you can get them. But, I put an 8X6 SEF on my DFX and get 7" to 8" with it. The stock 9.5" coil is a little deeper - 9" to 9.5" in my soil. However, it can't handle the trash like the SEF can, so it stays home.
Since you want a larger, deeper coil, I'm assuming that you are hunting relics or caches. You might look at the 15X12 or the 18X15 for those kind of applications. If you just want a deeper coil for coin and jewelry seeking, try the 12X10.
HH