If you mean not having to slow your sweep down too much to sort through the trash by using a fast machine, and if you want to save a few bucks, then look into a used QXT (the Pro version is the same machine too). It's computerized but with not a lot of heavy software, so it's a very fast machine for it's day, and will still hold it's own in terms of being able to swing fast against modern machines because it's got a very fast recovery speed. The added perk is the tone alerts are assignable to any of 8 zones on it, so you can set lows for stuff and highs for others and then just listen for any highs mixed in the lows. I never discriminated out anything including iron or the ground signal with it and just set highs for the stuff I wanted to pay attention to. Can't tell you how many old coins I've pulled out of junk with it not having to slow down my swing, and that's even with the stock 9.5" coil.
One of these days I'm going to stick another one back in my line up of machines with that little 4" or so hard to find trash coil that is smaller than the Bullseye that is more common. I think with a little coil smaller than the bullseye on that machine it would do some serious damage in trash or iron. I can unmask stuff with my slow machine and my 12x10 just as well, but fact is I've got to swing slow so recovery speed is a non-issue. Most days I'd rather swing slow anyway, but there are days I want to get up and move fast and that's where the QXT would come out when working heavy trash.
Think I'm finally home after a lot of years searching for my particular needs. Custom 1.5 lb lighter 
Sovereign GT (easy to do by just "building" lighter shaft) & SEF 12x10 as everyday coil. 8" Tornado (actually 7.25") as super heavy trash coil (Very deep & separates better than typical 8/9" true size coils). 13" Ultimate for large fields/beaches on certain days I want to grid faster than even the 12x10's nice improvement over stock for that. Stock 10" Tornado stays on water rig (stock shaft). 
ProPointer. Owned 15x12 & SunRay S-5 (5.5") at one time. Loaned a prior 13" Ultimate & SunRay S-12 (12.5").
Some Oldest Silver- 1835 Bust Dime, 1842 "O" Seated Dime, 1855 Seated Quarter, 1858 3 Cent Piece, 1891 Seated Dime, & another Seated Quarter too damaged to read date. Highest Value- 3 Cent Piece, Seated Quarter, & now 1921 F-12 Standing Liberty. Oldest Coin? Got to give large cents a good look & see. 2013 so far- 1 Seated Quarter, 1 Barber Quarter, 1 Standing Liberty, 2 Washingtons, 1 Barber Dime, 9 Mercs, 3 Rosies. 1 War Nickel. 19 silvers in total, & 1 1872 key date Indian, 2 Bufallos, 1 man's 14K gold medium sized ring & 1 gold chain, with possibility of few 8"+ deep mystery coins being Indians after cleaning.
What matters in life is the journey and not the desitination. How you handle that journey determines if you were a success, not so much what you achieved if and when you finally get there, especially if you made it by stepping on people along the way...
In loving memory of my long haired (wooly) husky Sky. She taught me just how beautiful and pure a soul can be, human or not...
V3i, 
Cibola/modified