Thanks Negakinu,
Much appreciated and from what I've read I am fairly sure, purely as a DAC comparison, either of the options I mentioned may outperform the E10 DAC but it is always good to hear first hand experience.
The O2/ODAC (sold by Epiphany acoustics here in the UK) would set me back nearly £200GBP which, given I have always been very happy with the X-Can V2 (in which I have some 'upgraded' tubes) is more than I would like to spend - in short, the amp section is of less importance to me at this time and 'one box vs. two' is not an issue.
The portable amp mentioned above would be for occasional work trips/office use etc but by far the biggest consideration for me is to have a 'nice' DAC to feed my existing amp from my (not heavily compressed) PC/NAS.
Of course, if that turns out not to be a good match then I will probably look to offload the x-canv2 and go with an O2/ODAC option or similar as you suggest but I'd like to try other options first (the lure of a bargain is strong

)
O.