Poor Quality Shimano Insdex shifter

I've been having a few problems with the deralieurs (It this how you spell it?) and have been
buggering about with the adjuster screws for weeks, never seeming to get it just right. Untill
yesterday when I finally discovered it's the indexer, not the deralieur. Shimano have not trimmed
the cable sheath properly so there were a dozen or so sheath wires sticking into the indexer
mechanism, with the result that it often didn't index at all. After a bit of work with the dremmel
its working pretty well now but I can't engage top gear. (I think the mechanism is damaged slightly)
If I decide to replace it what would anyone reccommend in the not too pricey range? (It's a hardtail
mountain bike) Thanks for your views in advance Antony

 

I've used the same Shimano Deore derailleur for the past year and a half and it's served me very well - hasn't let me down yet and I've used the bike more or less every day.

The same cannot be said for the brake levers though.