The problem is that many of us overload ourselves with a multitude of equipment we understand very poorly, rather than sticking to a couple of well-chosen pieces of kit, and getting intimate with them.

Truth be told, those of us with a half dozen keyboards or more could strip it down to two, and probably not lose an iota of sound possibilities. Most modern keyboards, arranger AND workstation, are so good and versatile that with patience and programming they are capable of just about anything you want. But we have this tendency to get just ONE more, just for this or that sound (which could probably be gotten close to on a keyboard we already own). and quickly end up swamping ourselves with manuals and confusing contrary OSs, that take very different paths to the same end.

Probably for all but those working at the highest levels in recording, one TOTL arranger and one TOTL workstation ought to be capable of just about anything our twisted minds can come up with... And mastering just two pieces of kit is a LOT easier than wrestling a big rig into submission.

I recommend they be from different manufacturers, to maximize your sonic pallet - maybe a G70 and a Kurzweil (my choice at the moment), or a PA2X/800 with a MotifXS, maybe an S900 with a Triton for those on a budget. If you can't make very professional sounding music with just the two, adding more is probably not going to help!

Avoid 'manual overload' and you get an awful lot more done!