this topic has come up on my site many times over the years, and the general consensus is:
1. generally best to keep an undershirt hidden
2. for one with a lot of chest hair or who wants to hide a tattoo, a showing undershirt is better than not
3. wearing a colored undershirt / t-shirt that has a complimentary color to the outer shirt can be a reasonable alternative to a plain white t-shirt
4. if the undershirt does show, it should be clean, and have a crisp collar that lays flat
5. use your best judgment on what you feel comfortable with from a style point of view. there are many socially acceptable ways to wear your clothing, but keep in mind that stylish men in forums like these will likely recommend a more optimal look, than a socially acceptable one.
i for one like the idea of wearing a button shirt with a collar underneath a v-neck sweater like this. i think that would look nice, and the collared button up would substitute as your undershirt.
if you do have a large amount of chest hair though, you might consider doing a little manscaping.
one reference article suggestion: search for "undershirts under v-neck" on my website undershirtguy [dot] com and you'll find a interesting article i wrote back in november 2009 about this very topic of wearing undershirts under v-neck sweaters.