My opinion:
The bass isn't bad. Subs are good. Mids (a wide Q around 300hz) are not really all that necessary. I've been removing that a lot in recent mixes because it's more or less a junk frequency in my opinion. You can use it, and that's not a problem at all. It more or less changes the "body" of the bass, without it you'll have a good low sound with a boost around 800Hz for the finger/pick sound. Anything above 2KHz is also unnecessary unless you want an unpleasant (again, in my opinion) click. Not a big fan of the click. It's a bass, get your clicking from the picks on the rhythm guitars.
Here's the EQ I used on "My Choice", which wasn't a metal song, but I'd probably use the same type of EQ for a metal song. This isn't for people to copy, it's just a guideline because honestly all bass sounds are going to be different, and from my understanding of Shreddage Bass you probably won't be able to EQ it exactly like a real, organic bass anyway. But this is a good place to start.
Should you double it with a synth bass? It depends on if it sounds good. Is it necessary? Probably not.
As for moving the kick boost frequency to around 60Hz -- not a bad idea if you want sub thump. If you want sub bass, I wouldn't recommend doing them both in the subs. Try 80hz for the kick. Some people can't even hear notes below 50Hz and they don't find that out until they use headphones. Anyone can "feel" a 32Hz note, but very few can actually hear it. That's scieeence! So I wouldn't bank on the subs in that way, I always try to get some kind of mid/higher EQ in there so things can be heard apart from just in the subs.
As for the guitars, do you have some kind of high pass on them? They're missing low mids. Try boosting around 170Hz for fullness. Don't do it a lot, because that will lead directly to mud, or being TOO bassy. Just enough to give them body. You can slope off the low shelf around 100hz also, instead of high passing, if you have uncontrolled rumble down there for whatever reason. (Edit: I'm talking like a -2db slope off in the low shelf, not a cliff!)
In conclusion, are you focusing on the metal, or on the "drum and bass"? At the moment it feels like you could put a better emphasis on the metal (thus my guitar suggestions concerning giving them more lows)