Yeah, 50k miles, it's new plug time. Unless you go with a big catless dp/rp (which would raise boost about 2 psi), you should probably stick with the stock heat range plugs. HT's tune is based on stock heat range. I went with the colder plugs just to provide a little extra protection against detonation. Probably didn't quite need them yet. Usually have to be close to 50 hp up over stock to justify the colder step. But they are not fouling. I drive this car pretty hard. So you could probably go either way and be fine.
One sort of crazy thing is that the colder plugs (in my sig) are readily available at most auto parts stores and are cheaper than the stock range plugs, which seem not to be used in any other applications and are, thus less popular, less readily available and more expensive! If you go with the NGK's (my personal preference, although the Densos seem to do fine), they will come with a huge .045 gap and will need to be gapped down. Either way, be sure to get fine wire iridium center electrode plugs, which are much more appropriate for high boost, high compression, DISI engines. Stay away from the platinums or multi-tip types.