203 at 20% means 160lbs of LBM, so if he diets to 14% it will leave him at 5'10 180. Now Rusty i know you have dieted before, the first 7-14 days depending one typically drops a shit ton of weight thats not fat, or muscle, just water from less carbs holding water, less water from cleaning up the diet (less sodium) less glycogen stores, and less overall food in ones stomach an gi track from eating less, And this weight loss is typically anywhere from 7-12lbs and bodyfat does not change during this time. So if OP has just begun his diet or not even started and not gone thoough this phase that could drop him to 193 at the same bodyfat, and if he didnt lose a single pound of muscle that would put him at 5'10 170 at 14%, a little light to be using gear.

Now to OP:
a routine full of compound movements is absolutely great, deads, bench, squats, pullups, dips, thats how you build a base, thats what I spent my first two years doing twice a week ( with some curls for the gurls ofcourse lol) But its just that, a beginner routine, to build a base and based off these stats I dont think you have that base quite yet. Steroids should be implemented when you already have a pretty advanced physique, ( that was kinda lost in newer generation) to push past plateaus that is just not possible naturally. Or at the very least when you have a strong base built, which i think youre still in the process of doing based off your stats. Now alot of guys here have unrealistic expectations of how big one can get naturally. Theres alot of stats and info compilied over the last 40 years but at youre height at 10% you should be able to reach somewhere between 185-195lbs ( higher weight based off bigger joints bigger frame, and taken from genetically elite) so at 14% you should be able to reach your exact bodyweight now of 203lbs at 14%, actually more based on the statistics and data collected.

So all in all, I think spending a year with a perfect diet building that solid foundation, getting your LBM and bodyweight up to those numbers I just talked about would greatly benefit you before using gear. Theres no side effects to natural training, the muscle actually says as its gained over a peroid that gives your body time to get used to it, compared to gaining X amount of size in a short 10 week window where after youre fighthing tooth and nail with your body to hold the size, it wants to go back to normal and you want to keep the gains etc. So dropping 20lbs of fat, while doing those compound movements, being at the stage youre at you should be able to actually add some size while losing fat. And then when the fats gone slowly add cals until youre in a 300-500 cal surplus and continue on with that routine full of big hormone releasing compound movements, and build yourself back up to 200 at 12-14% bf. And then if youre still not happy think about running gear. Obviously make changes to the routine from time to time to avoid your body getting used to it, but these routines are great. Many many of the great bodybuilers came from powerlifting style backrounds, arnold, franco, ronnie to name a few.

thats my 2 cents. remember you need to build a foundation before building the house.