Good Bench. And now your on the verge of breaking that mental barrier of 400, for in fact, that's all it is. I think the key here, for you, is your not being too consumed with a big bench but approach it in a logical way. You didn't give a complete sample of all the exercises you do (set's/reps) but whatever your doing is working . Not going to a max too often is a good idea, as is not going to complete failure on every set of every workout. PL's usually test their max every 3 to 4 weeks if progress is steady. Periodization is popular amoung some of these top lifters.
If you do slow down at any point in your training, after you get beyond 400, than you might consider power rack partials. Usually using the three pin positions. Has helped a lot of guy's I've known. In the top position (lockouts..3-4 inches) you should be using 100 to 150lbs over your best bench. This tends to set the body up to handle greater loads in the regular BP. Also PBN's and dips (weighted) have a very positive influence on getting a bigger bench.
As with using a power rack and/or chains: the more distance traveled in a bench (or most any other exercise) the more load is put upon the muscle group. My personal view (for what's it's worth) is power rack training would be a better option at this time. Chain training can improve speed/timing (very important) but does not tap the full potentional of power that a power rack does. Good Luck.
