Myself - I'd sell the 10" x 12" SEF and get a small coil ( 7" or smaller ) for hunting in heavy iron and in overgrown areas.
The 6" x 8" is a excellent coil but - it's not a small coil - many user's believe that the 6" x 8" hits as deep or almost as deep as the stock 10" Pro Coil.
A small coil like the 5.5" Sunray - 6" or 4.5" x 7" Excellerator coils are killer in heavy iron, great separation, real good depth ( 8" Dimes ) and don't hang up on brush like the open spoke coils !
I hunt with a small coil 90% + of the time - well over 1000 hrs. over the last few years - the 6" or 4.5" x 7" Excellerator coils are nothing short of fantastic !
If you had a small coil you would have all three sizes for your machine and you would be well prepared to hunt any type of site.
Here's a link that Bryce Brown - ( Moderator of the Findmall Explorer forum ) posted on field tests of many different coils he's used.
A ton of great info. here ! >>> http://www.findmall.com/read.php?19,1055627
Good Luck !