There are alot of good options for you Max in here. Another thing you want to consider is running a stim side by side with this product. Synephrine or Ephedrine especially works VERY well for competing.
And it's all about the timing of these products when looking for strength. You want to dose these in a larger dosage all at once when looking for strength gains. You simply don't jack up your caloric intake much if you want to remain in the same class. Or simply put, eat very clean and don't try to bulk.
One can use abombs to lean out if you are in a calorie deficit and do it right.
I will let you in on a little secret combo that I suggested to the guys I prep for PL. I have them use EPI ANDRO/Furazabol/Epistane and ECA. (you could always plug Ment or Trest in but those are wet compounds and are more likely to add some water weight that you dont want)
I liked them to use 200 mgs of Epi andro (so modular series can work) , 45mgs of Epistane, 50mgs of furaza (the right version LGI or olympus versions are solid) and then EPH at 50mgs, 200 caffeine, 81 aspirin. You want to empty the caps and pour them into your mouth. The solid pills, chew up. Then do your workout about 30-60 mins later. It is about hitting the "peak" of the synergy of these products. So you can even get away with 1-2 hours later.
Just watch the spikes in blood pressure from such a combo, so if need be, work up to this dosaging wise, meaning if you have to, start with lower milligram amounts and go up little by little til you find your sweet spot. Don't go too high..as more is not always better and dont overdo the ECA either..that can be dangerous. Use this like you would a preworkout, stick with heavy dosages prior to the Powerlifting day or meet, etc..and on off days, do even half the dosage, leave out the ECA.
The thought process behind my protocol is that it will give you a super strong synergystic effect and the ECA and dry compounds will eliminate water through constant urination, and make it so you are not making Huge size and bodyweight gains . Likewise lowering the dosage on OFF days, still allows you to keep a steady blood plasma level, so you want smaller dosages more often on your off days, do not dose it in one shot.
And no ECA on off days, because you do become immune to those products and can even show adrenal fatigue, etc..from constant stim use..so be sure to leave this ONLY for preworkout purposes. EPH has HUGE spikes in strength and this is why you will see often sprinters will use this or synephrine or other stims for explosive power, like you want in Powerlifting.
If I had to choose one compound, like H2s said, higher dose epi in my opinion works the best..based on a few years of experience with alot of pro and amateur powerlifters. This is the compound I found to be most effective hands down and showed the biggest strength gains in the shortest period of time, all the while keeping size and bodyweight gain to a minimum.
Remember this is all about strategy. This is effectively the same thing as "nutrient timing" only the nutrients are supplements instead of food. It makes all the difference in the world, don't let anyone tell you different.
The worst possible effect of this combo would be the spikes in Blood Pressure that are possible. Also anger/aggression might be an issue if you use this protocol I personally designed years ago. When done properly it works like a charm