Excellent question -two recent experiences of mine tie in with this; purchasing a new cornet and a new trombone.
I have been playing cornet for 2.5 years, and am happy with the model I have - a short cornet, but wanted a long cornet (which can have a more focussed sound not unlike Miles Davis's Martin Committee Trumpet) and recently tried two different models - a Yamaha and a Conn. I could tell instantly that the Yamaha was not a satisfactory instrument for me (in fact it is rated a high quality beginners instrument at £550 new) but that the Conn was brilliant soundwise (secondhand at £612). Similarly with a recent trombone purchase, where I could quickly appreciate that the more pro quality instrument - Olds Super from 1950 - had a depth and complexity of sound that my more student rated 'bone lacked, even though it was me doing the blowing on both.
What I conclude is that I wondered about trying something different and then could instantly tell by sound produced that I could benefit/be more satisfied from a higher quality instrument. What was good was to realise that my short model cornet compared very satisfactorily to my new Conn Connstellation 38A(1960).
So it may be that a combination of some questioning of what you currently play together with some trialling of other instruments should provide a ready answer to your question. If not, you are probably not at a sufficient standard play wise and/or listening wise to need an update. Clearly with the trombone above, even though I have only been playing a month my sound facility has developed significantly over the past 3 years, since starting Sax etc. and that my tone was already developing well (according to my teacher).
Pete's post is very true in my opinion, above and beyond any GAS tendencies that many of us might experience from time to time. We may each have some inkling that a change is in the air/needed - we are after a certain sound, or have some sense of what we are searching for, and have to satisfy that need in some way.
Kind regards
Tom
