I'd still say there was room for a bit of a volume increase. I can switch my monitors off and turn my sub up to full and still it doesn't shake the room (which it should at that volume). I realise though you say this is unmastered and the levels are a little bit lower generally on the track than I would expect, but even allowing for that I'd say you could increase the volume still. Also, this might be Captain obvious but make sure you have positioned/calibrated your sub as best you can, if not you run the risk that your sub is louder or quieter than it should be. The other way is simply to reference (which i try to do allot), switch off your monitors and play a track from one of your favourite artists, then play your track and see how your sub volume compares (you have to be careful though to recognise your levels are still a bit low as it's unmastered, I use a cheap sound level meter to make sure, I aim for a monitoring level of around 85 db at peak).
The other thing you can do is to consider adding another synth and EQ it for the mid range (aiming for around 2K-6K ish but go with what sounds good and 'glued' together) to give you some more mids and layers, but that will change the sound/feel quite a bit.
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