Hegel H160 -> Hegel H390 upgrade suggestion

+1 on a second sub either way, as @soix has stated.  

but do you think a second sub would make that much of a difference when the lower frequencies are directionless anyways?

This is sort of true.  Very very low bass can be directionless.  Try this: stand in your room, close your eyes, and point to the sub.  You can pick out a single sub almost every time.  Having two subs allows the integration to be almost seamless.  I am a REL fan, but you can integrate most subs easily.  First, set each sub's phase for maximum bass response.  They may be different  Then, set the sub volume where you can hear it,  and adjust the low frequencies until they just disappear.  Then turn down the volume until you can barely hear it.  do this one at a time; you may need to go back and forth a bit.  Properly adjusted, not only will the bass fill in the lows, it will more effectively support the soundstage and improve the midrange of your speakers. And they will disappear much more readily.  At least this all did for me.  You may even find experimenting with different sub positions helps.  

@fastfreight I guess I should try that with one sub like you advised and then get the second one as advised. I never thought of adjustment in that sense ever honestly.

REL has a nice little video on sub integration.

@fastfreight thanks will dig it out tonight and give it a shot for sure.

Do not confuse speaker "rated" power with what you need.  Do they play loud enough for you?  Any hint of clipping on a loud transient? Cymbal crash etc? Be realistic in the peak level you actually play at. Movie special effects or symphony front row?  WHO concert level?  ( For the latter case you probably have hearing damage and it does not matter) 

You can get an idea by using various on-line calculators that input speaker efficiency, listening distance, desired overhead, etc.  Decent understanding, but it does not take into account the effective impedance, and hence current requirement due to phase vs impedance.  Some speakers, like the Keff R3 are absolutely brutal and bigger power is needed.

I run my bookshelves in a large room with a 60W MOSFET with a HUGE power supply and filter bank.  For fun, I tried my Schiit REKKR  (2W) and it did folk music just fine. I also tried my workshop amp, FOSI V3 which is in reality about 30W and it fell on it's face, not for power, but for load variance issues. Well, it is an $80 amp!

You can also give the Hegel power supply some breathing room by putting a good correctly sized cap in-line with the amp input.  Depending on input impedance, give a 20 Hz first order roll-off.  This will help with reducing compression from transients, though the Hegel does have a decent power supply. Far more critical on a Rotel or something where the forgot about putting in filter caps.

I also support multiple subs. Not for power, punch, or distortion, but for smoothing out the room nodes.  A single 12 will play loud enough to bust your ear drums. It is smoothing the response that matters. 

Any wavelength smaller than the box dimension is basically omnidirectional.  Just to be clear. 

FORGET all that, and dump the 160 to me for a couple hundred bucks  and buy a 1000W Crown :)