rklein,
i'm not a home theater expert.. but I think the front three channels are far more important than the rear surrounds (which your nht speakers seem more than adequate for). If I were you, I'd go with your second idea and buy the khartago/etesian combo-this should be a significant improvement over your marantz receiver and if you want, you can use those channels for other purposes. give klaus a call-he should be able to do an av pass through on the etesian. keep us posted on what you decide. good luck.