Ron, iBasso and your good self are really endangering my newfound fiscal restraint. Clearly, its a conspiracy. 
You may recall that I expressed interest in pairing the D12 with the P4, even after my original P4 had gone to the great amp retirement home in the sky, on the basis that I would have a 'very-good-DAC' with a 'very-good-amp' (IMO, the P4 is the best single-ended iBasso portable amp, but I haven't heard the D6).
From your impressions, it would appear that the D7 represents a cheaper route to similar audio nirvana, even if I have no immediate need for 24/192 capability beyond a few audiophile downloads that I rarely bother with.
However, I know that as soon as I get my debit Mastercard out I will uncork the genie which tells me that the only way to really to justice to such a combination (D7+P4) would be with a set of IEMs in the Westone4 / GR10 bracket. All up, well over 800 AUD delivered. Ouch - this is the point where critics of portable audio begin to bray annoyingly in one's ear. 
I know - men, boys and the size of their toys - but right now I'm going to hold off and see where iBasso go with the DX100. Thanks for your detailed impressions on the D7 - incredibly tempting and I reserve the right to change (or lose) my mind between now and the March/April DX100 release. Sure, I'll end up spending that $800, and then some, but at least I can kid myself that I 'held out' for a few months. 
estreeter
