Descrimination is very usefull, I can reccomend any of the Minelab Series of detectors, for Relic Hunting I use a X-Terra 705 (which is basically the same as the previous model X-Terra 70) and for deep and precise I use a Minelab E-trac.
The benefits of the Etrac are simple, (once you have overcome the learning curve, you will know what to dig and when), its more suited to finding deep buried coins than relics, you can locate a buried silver coin from underneath a fair sized piece of Iron.
For a reasonably priced relic only machine with adequate discrimination that is easy to use and enables you to discriminate out the 303s, 9mm and fair size pieces of shell fragments (I have a shed full allready and am way past the excitement so to speak, dont get me wrong, I always take them home if they come up!) the Minelab X-Terra 50 or 505 series upwards is an ideal machine.
Allways dig those large overload signals whenever you get them, yes it could be a wire picket, or it just might be something special.
Buy the best quality batteries you can afford and allways carry a spare set with you.
Good Luck. Andy.