The Silverbullet and the Provari are great mods. I have had no issues with them.
Cant help you with the carto issue cuz I think cartos suck. I only use attys.
That is what is known as a "wick" . Brand new its white and overtime it becomes brownish, sometimes black, due to the juice and heat. That could be the culprit of your bad tasting atty.
You can try de-wicking the atty:
I got mine about a year ago and they are still lasting me a day. But I only use them at night and on the weekends. I use my eGo the most since thats what I use at work.
You can pick up a blemished Infinity for around that: http://www.notcigs.com/infinity-pro/ . Its a variable voltage device that gets good reviews. Don't forget to pick up a couple of batts and a charger. Oh and as far as the VG juice. I use VG with my attys when direct dripping.
They both get good reviews. I would recommend getting a blemished one to save a few bucks. I believe you can only use the reg cartos on the 1" tank and have to use the XL's on the 1.5" tanks. You should contact them to clarify.
Upping your nic level may give you the satisfaction you are looking for. How many packs a day did you smoke? Are you looking for an e-cig that will help produce a lot of vapor, or is your 808 satisfying?