A larger enclosure has nothing to do with "thunderous bass" .Some drivers work well in small enclosures, the type r just isn't one of them. The increase in power has nothing to do with it's output level, sure it may yield an increase in overall spl if you want it to and if that is your goal, but it's about how the driver behaves, and it is far more controlled with the extra power behind it.
A sealed enclosure will require more power before reaching xmax, the driver will not reach xmax in it's current enclosure, with 500 watts, therefore it is not performing at it's best, and for a novice you also risk clipping the amp. Again at it's best doesn't mean as loud as it's capable of playing. If you wish to put a driver in an enclosure that is not suited to for most of the part, then that's completely up to you. You could compare it to the rest of the instal, you can spend as much as you like, but a poor quality instal or badly chosen component then what's the point?
The MRX range isn't moving down in quality compared to what he is spending on the drivers. The drivers themselves will always have the biggest overall difference in the end result. A set of $800 speakers with a $200 amp will sound better than a set of $500 speakers with a $500 amp, or any other combination you want to throw together. That is why the MRX range are more than up to the task of powering the type x. Plenty of people also do well with the mrx range in sq events, yes the pdx range do well also, but what does it say about the lesser spec model for those who chose to use it and did well?
Peace out :smoking: