I know this isn't what you want to hear
because even though you are wary of how to spend the money, the fact is you've got $300 burning a hole in your pocket. ( My dad is laughing somewhere, knowing that I just said that
) You desperately want to buy some gear.
OK, I haven't heard your stuff and I don't know your whole setup including methods etc., so I suppose I can't really say with certainty what's the best next step, but here's my best guess: room treatment.
One thing I'm definitely developing an opinion on. You've undoubtedly heard it said that someone with skill can make a better recording with crappy equipment than someone without skill can with great equipment. I'm increasingly becoming aware that the same individual can make a better recording with crappy gear in a great sounding room than he can with great gear in a crappy sounding room.
Or maybe not, but it sure seems that way to me. As they say, garbage in=garbage out.
Now I know, it's not as much fun to show off your broadband absorbers as it is your new KSM32, but you've got to decide what you want to do - make better recordings, or show off to your friends.
And I'm not picking on you, because the vast majority of us here (myself included), no matter what our age, are guilty of the same thing from time to time. We'd rather have cool new wheels for our shiny badass truck than more money in our 401k. You can't show off your 401k to your friends, but if you're smart, that's where it will go.
Anyway, maybe you've already got the treatment thing covered and I just wasted more time and bandwidth, but if not you, then I'm sure somebody out there needed to hear this.
Not that anyone will listen.
Off to the basement for me. Time to work on the 'studio'.