I would give cartotanks a try.
I haven't tried the Kanger ProTank yet, but I've tried other string-wicked delivery devices like clearomizers and Vivi Nova
tanks. I've generally been disappointed with their flavor production and consistancy. Plus, I find needing to tip or swirl the things to keep the wicks wet annoying.
Cartotanks are not position dependent. I find they give me noticably better flavor. They take a little longer to set up, but to me the time is worth it in the long run. They also have a slight learning curve, but when you find a filling method that works for you and perhaps adjust your vape technique, your patience will be rewarded.
I suggest checking out
IBTanked - Get Tanked With Us!. You can get a high quality pyrex cartotank kit with metal endcaps (stainless steel or anodized aluminum) for under $30, possibly less.
I have seven currently, and did a review of them here:
http://www.e-cigarette-forum.com/forum/blogs/baditude/3318-3-ibtanked-pyrex-glass-tanks-review.html
This is a cartotank tutorial that I wrote:
http://www.e-cigarette-forum.com/forum/blogs/baditude/3710-5-cartomizer-tank-setup.html
IBTanks on an eGo, a Provari, and a Silver Bullet