if you are going to grind up cash games then i think you should employ proper bankroll management and play the limits you are "rolled for. 4 buyins at 25nl is playing with scared money and you could get your chips in as 70% fav and lose them all = busto. Plus not reloading when busted and things such as that are not good for long term profit, especially if a fish has just 2 outered you and you have good expectation if you reload.
even playing well, 10 buy in downswings are not uncommon, therefore your bankroll has to be sufficient to cope with this.
for this reason i would continue grinding 25nl with the "roll you have until you have at least $1k. Even $1k can be a small roll for 50nl, but i guess you play kind of conservative compared to me (and i assume full ring as opposed to 6max tables)