Actually, properly implemented oversampling by sinx/x convolution (or FIR filtering) adds absolutely nothing to the signal... one of the great beauties of working in the digital domain. Oversampling doesn't work so well when the digital filter is compromised by economic decisions which will tend to decrease the number of "taps" used in the filter, and hence the ultimate quality of the interpolation. Anyway, a well implemented interpolation filter will spit out the original samples with nothing more than some extra samples added in between... samples which follow precisely the curve of the signal (eg. the technique is not an approximation method) - no phase shift, no frequency response changes, no added signals, nothing subtracted. I guess unless you have a really intuitive understanding of the algorithm and how it works, it's perhaps difficult to visualize this, so you'll have to take my word for it...
If you have any doubts about what an oversampling interpolation filter does to the signal, you'd be absolutely flabbergasted by what happens inside a sigma-delta DAC. These little buggers "throw away" the vast bulk of the original signal's resolution (ever hear the term "1-bit"?), and add huge amounts of frequency-shaped pseudo-random noise... yes *noise* (it's all ultrasonic, and gets filtered out in the analog domain), while oversampling and "interpolating" up to 128 times!!! What's more, most bitstream type DACs use various feedback techniques to correct and linearize the output. Anyway, what comes out the other side of a sigma delta dac isn't anything even remotely resembling the original input samples, and yet the best sigma-delta DACs are audiophile-approved (eg CS43122)... in fact, 99% of the DACs you hear on a daily basis are probably sigma-delta types because they're much cheaper to manufacture.
Anyway, my point is, the minimal and very benign processing done to accomplish simple oversampling interpolation is absolutely nothing to worry about, and reports of "audible" effects are quite exaggerated (though I won't say false - since practical FIR filters aren't *quite* perfect, and there are bad filters). All that oversampling does is deliver a much smoother output signal, so that a simpler analog filter can be used... thus relieving the potential for much greater sonic damage caused by a high-order analog filter. To be honest, i am amazed and dismayed at the fascination with non-oversampling, unfiltered DACs, and the piles of baseless "evidence" supporting the belief that they are sonically superior. So far, i have never seen a valid argument why interpolation should produce any negative sonic effects.
My advice: go for a good 8x oversampling chip (NPC, DF1704/1706, or PMD100 if you can get one), and use a low-order analog ultrasonic filter centered at say 60kHz. I wouldn't risk going filterless (oversampling or not), as you risk sending high-level ultrasonic trash to your subsequent amps / speakers and causing unnecessary distortion or damage.