Rule out using the D2 Stock coil for trashy or target rich areas.
The 6X10 is pretty good. I used it this morning and found a silver coin in iron about 2" down and it rang solid (dime thickness but half the size). The iron was so heavy that I couldn't ground balance anywhere! Luckily my last GB worked fine. I also found a button and large coin and some WWII bullets.
I also have the 5" Excelerator coil. This coil works great in trash and irony sites, but don't plan to cover a lot of area. It is better than the 6X10 coil when targets are close, though the 6X10 coil does separate you are overwhelmed with signals. I've pulled coins from an iron rich area with the 5" that the 6X10 didn't hit on. Now, my 5" is not a V certified coil but I can max out the sensitivity. But, why would I want to do that in iron or trash? First, I found that the coil hits 1.5" to 2" wider than the coil with the Rx at 8 and up. At 6 it has no real edge effect, so in trash, that is where I run it to keep things quiet and also to improve separation. It still will go at least 5", if not 7" judging by the solid hits. I use it in 3 frequencies mostly, but through testing found the 22.5 Hz works better on small thin hammered coins (which is equal to some small jewelery I'd imagine.)
So, if the trash gets bad I wouldn't recommend the 6X10. I think the 6X10 is a great main coil to use if there is a fair amount of iron or trash. That said, the depth is probably 2" or 3" within the stock coil. (Can anyone confirm this?). That amounts to 9" or 10" easy on coins.
I would recommend the 5" or the 4X6 Whites Shooter coil. I would like to try the 4X6 to see how it compares to the 5" but am sure they are pretty darn close.
Good Luck,
EMS