You can upgrade the 6xp to the 'd' variant for about £400. Or you could look at an external DAC - Rega/Dac Magic et al at between £300 to £500, which I'd imagine would give you far more value.
You can then connect your ipod via, for example, an Onkyo ND-S1 (£100) to the DAC. This would give you a neat set-up.
The Audiolab 8200cd gives you the best of both worlds as you can connect your ipod to it via an Onkyo (or similar) and you also have the cd player facility.
Personally I'd go for the Audiolab option, as it has a number of digital inputs, a high quality DAC set-up and a cd player, albeit more expensive than the other two options. If you don't want the cd player option, I'd be more inclined to look at an external DAC solution.