I actually own the R12, and if you can stretch the budget, I'd say go for it over the R9.

The main difference is "headroom." With the R9, you're often running it near max power to get good detail, which can cause clipping. With the R12, you have that extra power in reserve, so the details feel cleaner and the wheel doesn't get as hot. It's definitely worth the extra cash if you want a base you won't need to upgrade later.