Okay so whatever that is, it's quite elderly, and you aren't likely to get more vapor out of it.
The amount of vapor depends on a lot of factors, not just the resistance of your coil. Quick definition: Sub0hming means using a coil that is less than 1.0 ohms resistance. Usually used by those who like a quick, direct inhale into the lungs very fast, usually uses lower nic juices and higher VG ratio, and more airflow.
You can still get plenty cloudy without using a sub0hm tank. Variable wattages, airflows and types of juice all play a role. For example, I am NOT usually a sub0hm vaper, but I still get more clouds than the average MTL vaper, as I can only use 100% VG, I'm sensitive to inhaled PG. I minimize my watts and airflow and still am able to get clouds and if I wanted to, I could up my watts and adjust my airflow to really get a restricted Direct Lung hit, should I so choose. I do not so choose because it's not my vaping style. I vape at 7 watts and at the most restricted airflow setting I can, and I am plenty happy. I use coils usually around 0.7 (can still manufacture a Mouth to lung hit with that coil) to 1.8, max, and it more closely mimics smoking for me, and I enjoy that style of vaping more.
The advantages of MTL (if you like it) is it uses less battery, less e-juice, and one can go higher nicotine on such a device. Believe me, if you use newer equipment, you may still find yourself producing more vapor than you are used to. I'd strongly consider a MTL setup that's maybe a crossover tank to start. For example, a Nautilus 2 tank, which will arrive with a 1.8 coil and a 0.7 coil, so you can try out restricted DL hits by playing with wattage and airflow. It will be less expensive, and still a vast step up from what you have now. You can buy a mod that is still a tube type mod with enough power to attempt a true sub0hm tank for down the line if you want. I won't get into recommendations on that as they are so many and so vast.
That would be my recommendation, but if the idea of huge clouds appeals to you, by all means investigate and purchase a true sub0hm setup, if you are dying for vast clouds and the idea of Direct Lung hits appeals to you. I'd search around on the boards and look at some setups at least on line, and in person if you can.
Best of luck!
Anna