You have done a great job with the tracking and remember I'm not a professional mastering house....(but a lowly underpaid and over worked scientist) !

It is difficult to get right in there without a multi-track and remember I don't really know what the final sound you are after is.

There is a lot of signal between 86 and 170 Hz and not much between 170 and 340. This effect of scooping your bottom mid is making you sound a little thin despite the fact that there is loads of bass. However, you need to be careful boosting this region (or cutting some of the bass) as just EQing the mix changes the character of the track too much (or I'd a posted it). I'd have a go at tweaking all individual tracks (more low mids less bass) with the exception of the rhythm guitar mids (as that is too prominant and a deal breaker) in the hope of fleshing it out a bit more.

Hope this is helpful. Do you use Wave lab ? Waves plug-ins ? They are great even as just analysis tools to look at your frequency spectrum.

I'd still buy some flat response near-field monitors !
(cheeky northern b****** that I am !!!)