Mixing and mastering with sub woofer ?

Yes, I did exactly that.  If you hear clear bass on your mix at home, you won't mix bass up so high.  

I do use a reference track...i will look into sonar works..im thinking its my monitor placement..ty for replies

I do mix in stereo..i did add a sub but its only one side, seeing that my kick and bass are centered i know its not the best way to do it but my thinking is it will help me get that bassiness in mix down..my question is..can you elaborate on your last sentence about it not translating properly

^^^ +1
 
If your room isn't well-treated, a sub can just complicate things. Many of them come equipped with a bypass footswitch jack so that they can be easily taken out of circuit while mixing. It's a good feature to look for when shopping for a subwoofer.
 
But before you start shopping, do some basic testing to see if you even need one. Start by measuring your speakers' frequency response. All you need is a clean sine wave audio source and a microphone to record the speakers' output. What you'll observe is that output will start to drop off dramatically at some frequency. Find that frequency and compare it to where the musical meat of the low end lives, around 60-80 Hz. If your speakers drop out at, say, 50 Hz, then I'd say you probably don't need a subwoofer. Don't worry that they don't go down to 30 or 40 Hz, that is not going to ruin your mixes.
 
So what to make of it if your speakers seem adequate but you still have translation issues? In that case it's not about what you can or cannot hear, but rather about the evenness of what you hear. Not just in your studio space, but also in the other environments you're comparing against. It's almost never a speaker issue, but rather an acoustical one.
 
Cars have the worst acoustics outside of a drain pipe, so be careful about conclusions based on car tests.
 
I transferred my room test sine waves to a CD so that I could take them out to the car. I drove my car around to the back of my garage studio so that a mic cable would reach it, then stuck a boom through the driver-side window so the microphone was positioned at ear level. I then played back the CD and recorded the output.
 
I expected it to be awful, but wasn't prepared for just how bad it really was: 30 dB peaks and valleys, and a huge bump at 120 Hz. And it wasn't just low frequencies that were seriously messed up. Comb filtering from tweeters aimed at the windshield sent the frequency response all over the place. Mastering a mix so it sounds OK in the car is a worthy achievement, but ultimately means nothing because it will likely still sound bad in another car. More relevant to this topic, it would make no difference at all whether or not I used a subwoofer for mixing and mastering.

If you are a Sonar user, you have probably already signed up to Landr. I often use their service as a guide to my masters. I might not end up using them for the final mix, but they do give me something to work with. Izotope do something similar.
If you're mixing 'for' a subwoofer setup, you might want to get a decent subwoofer setup in your studio at the initial mix stage, master it down in the studio & then master another version using Landr (they usually take out some of the offending peaks and troughs and boost overall levels) and try listening in various cars and on various stereo systems to see which gives the best result.
 
An old friend of mine who studies at Paul Macartney's school of music in Liverpool used to always do the '**** tape recorder' test. We'd mix everything in his beautifully balanced study, then take the final recording downstairs to the communal kitchen area and play it on a crappy tape recorder. If it still sounded good, we knew we were on to something. Of course, we are talking of the days before digital....:D I do something similar now - I've got the headphone test, mono-speaker test - mp3 test - iphone test - car test - basically, I try to listen in as many environments as possible. If something jumps out during one of the test, I know something is up.