...and if you take a look at some of the ion related threads on speak to John C you'll notice that a QEV can make your marker a lot harder on paint and increase wear on some of the o-rings. it's a bit of a dilemma, better efficiency and quiter/smoother operation against added wear and having to use good brand paint rather than cheapo white-box stuff.
I picked up a firebolt with a marker purchase though you can find then on here from time to time for £15 - £20. Stock bolt you might get £5-10 but hardly worth selling at that price.
A chap on here can lighten the stock bolt for similar end results to having a firebolt , does it quite cheap too.