Its pretty much customary that over 450Fps you upgrade the sears, so for 400 I see no need.
I would personaly upgrade the cylinder and cylinder head, to increase compression, as well as the spring guide(you can never be to careful).
I havn't had any experience with TM stock chambers, bucking, and barrels; but if your keen on getting those instead of going for a Nine ball bucking and EdGi or like barrel then go for it, but again I don't know how stock TM components perform.
I would personaly upgrade the cylinder and cylinder head, to increase compression, as well as the spring guide(you can never be to careful).
I havn't had any experience with TM stock chambers, bucking, and barrels; but if your keen on getting those instead of going for a Nine ball bucking and EdGi or like barrel then go for it, but again I don't know how stock TM components perform.