Nah man, desensitization to aas is something that happens on cycle and then goes away. But it's a bit more complicated then that tbh...
In any case going 300mg test vs 500mg is for me not a big difference. I get more horny on 500 thats all. I would actually much rather add an oral to the cycle then up the test though. I would do it like this: 300mg test, 400mg eq, superdrol 10mg kicker first 4 weeks, tbol 40mg last 6 weeks.
More fun than just straight 300/600 t/eq
But 300/600 is also a good simple cycle imo for first time. I don't know however how androgenic eq is. How much it affects psycho functions... 600 might be abit over the safe side for a first cycle. Maybe 300/400 is a "safe" first cycle if you want to play it like that and then add an oral at the last 6 weeks if the results are underwhelming. Idk