I've had no problems with aluminium nipples, built carefully and looked after. If you like you could build the rear drive side with brass.
I think it's worth paying the extra for DT. There's a huge range of aluminium alloys available, and machining precision makes a big difference. The no-name eBay items may be of comparable quality, or they may not. It's not worth the hassle of rebuilding a pair of wheels for the price difference, IMO.