i think you mean twin tuner,this enables you to watch one channel while the recorder can record a different one.the size of the hard drive is important for the amount you can record, 160 Gb is good.Humax make a unit called the 9200, this unit is probably the best on the market. @ about �200.I have had one or two different makes and this is more reliable than most.
Digifusion make one that Sony Re badge but it is a bit quirky, the Digifusion is aroud �100 ,Sony (same unit) is �180!!!!
good luck,they are all handy units no tapes etc..