Hi, I was in the same budget range last year & went for a B&W ASW608 subwoofer, it cost me EUR 450 and the improvement in a 5.1 setup with BL3+BL4000 was amazing! B&W is a very respected manufacturer, and this new range of subwoofers has built-in ICE amplifiers !!
Mine is hidden under the bed, so design-wise there's no problem, although it is just a square box.
If you're looking for better looks, indeed the B&W PV1 is a reference, it never had any bad reviews and is also fitted with an ICE amplifier. But it is 3 times more expensive too..
Reunion Island is greeting you!