If you are using a single stage press you don't need a powder check die. Buy a reloading block or two. It is easy to visually inspect the powder level of your charged cases under a good light.
I decided to get one when I bought my first progressive press after hearing stories of squibs and overcharged handloads.
After some research I chose the RCBS lockout die. It does not require that you watch the die to determine the powder level. If it detects an improper level (too low or too high) it will STOP your press whether you are watching the little indicator rod or not. The first time it "worked" it surprised me. Turns out a .357 case had gotten mixed in with my .38s. The powder level was OK but the die "realized" the case was too long.
RCBS and Hornady make a die with a rod that indicates the powder level (RCBS is a Powder Check die, Hornady calls it a Powder Cop die). Midway had the Hornady on clearance last time I was on the website. Both are OK but they depend on the operator watching the die as the charged case goes through.
Dillon makes a powder checker but I'm not sure it is suitable for non-Dillon applications without some modification.