I'm a kpop coverist ^^ We use the two track instrumentals from the albums and such.Thanks to Mr. Bitflippers advice I can finally hear the mix better on my cellphone! I simply cut off all frequencies to about 70 and then boosted at around 45 with rbass during the mastering process, and put a low pass filter at 18khz. I added about 1db in the 9k to 12k range just to give it that Polish. There is a mastering template I use in Sonar--Mastering Template Smooth--in which the Sonitus EQ, COMPRESSOR, and phase are already tuned for a smooth master.

I added a waves L3 Multimaximizer and threshold is at 7.0 and output at about 0.3? There's no dithering since I don't fully know what that is yet, something about raising a noisefloor. I used waves Kramer Tape preset Big and Open, SSL comp and I'm doing some light compression on the entire track. I have taken some of the muddiness in the mid with FabFilter Pro-Q at about 3.5k and boosted at about 600k but only 2 decibels with a semi wide boost. I used Waves Lo-Air 5.1 for a more surround sound I believe and that's it. My mix was completely remix with a better reverb approach and less high passing. I only high passed my vocals but not the instrumental.

I simply put a small bassbump at about 121 and then added waves Center Stereo. I pulled down the center and pulled the sides just a bit and focused the bass to the center the highs to the sides and punch to the sides. I felt like the instrumental didn't need much since it was already compressed but needed to be open for my vocals to sit.

I usually overdo it but luckily I found a balance and my CPU wasn'to fighting for its life ^^

Knowing that you use finished tracks as your background makes much of the advice given sort of  guesswork.
That would have been the single most important information to start with in all of your posts, not just this thread. I assume all the folks here have thought you're trying to mix and master a "normal"  project. Everything you do, depends on what has been done to those background instrumentals, how they have been mastered. As you can't tell it, and we don't know, it's hard to start giving instructions.
 
Anyway, nice that you're getting the results you've been hunting for.
 

...and output at about 0.3

I assume you meant "-0.3". For MP3, I'd actually lower that limit a little, as the filters used in the encoding process tend to create high-frequency peaks that can easily exceed 0dB. Technically, to avoid intersample overs entirely you'd need to set the limit to -3dB, but that's a little too quiet for the genre. Try around -0.5 or -0.6.
 
One problem you may be dealing with is that the two-track mix you're using is already mastered to a high average level, and you're adding a vocal on top of an already-mastered music track. That's going to tend to result in a flat-sounding instrumental, so you need to use as light a hand as possible in order to avoid doing damage.
 
I've never tried what you're doing, but if I did I would "master" the vocal and instrumental components on separate busses and then combine them. That way, I could do anything I want to the vocals, including smashing them flat with a limiter, without hurting the backing track.