I have two of the Rythmik kits with the 370w amp. I have had them shut down twice in the last 2 years I've had them. Both times it was when listening to rock music with constant heavy bass for an extended period turned up loud. I felt the heatsink and it was very hot. The amp needs to shut down at this point to avoid damage.

Previously I ran a pair of 12" subs with a pro power amp - Behringer EP2500 with 650w into 4 ohms. It never ran out of steam.

If you are finding this is a problem all the time, then you are asking something out of the plate amps they aren't designed for. You have 3 options:

1. accept the limits of what you have (no, I didn't think you'd like that one)
2. use multiple subs
3. use an entry level pro amp - they are the cheapest way to get lots of power and they are designed for sustained high levels, but you will have fans to contend with

Plate amps are better for home theatre where the bass isn't constant. They are easily hidden in the sub box, have no noise and are an easy solution. But if you are a young single batchelor without WAF issues then a pro amp is the most fun you can have.

You can get plate amps with more power, but their cost is high. A 500w plate amp can cost you more than a pro amp which can easily give you 2.4kw bridged.

Now I run two Rythmik kits and find that if I want more steam, I'm going to need to turn my home theatre into a bomb shelter to keep the neighbours happy.