I bought a brand new Troy X5 about 10 years ago here in the UK,used it for a year with many hours on the clock and must admit just could not 'Gel' with the detector,its the only machine that i have ever sold and if i am honest i detested it,it just loved iron,must admit the only thing that i did like about it was the Fisher build quality.
When i bought mine i also bought the 10x6 coil and of course the stock 9'' coil,the 7'' one was the one that i really was after but just could not locate one,the 10x6 coil was on the detector almost all the time i used it,someone offered me a stupid high price for it and i jumped at the opportunity and dont think if i recall i lost any money when i sold it,which is very unusual as often detectors loose a massive amount,but because very few people owned them the price stood up very well for me.
At the time i fell for all the 'hype' of how good these detectors are depth wise etc,but how ever hard i tried to master it,its down fall was its liking for iron and on some of my roman/saxon sites they can have alot of iron,so sold it.
From my limited time with the X5 i liked the 10x6 coil the best,of course other may suggest differently and also say that the X5 is the best thing since sliced bread,alas it was not with me.