What firmware version are you on mate? Check if you can update your device and if; do so. Make sure you back up everything you need first, perform the update, reset the device with a soft reset again. Install the back ups, but do not install back ups of settings. Redo the settings manually.
The N97 has quite a few limits, but I never experienced issues with opening and using the photo album. But if you have tons of pictures, it might be that it's eating all of your RAM. Now, what I would do is to make sure that you close apps after using them. Make sure you exit apps and not just click the home button. The apps will still run and you will eventually run out of memory.
It could also be one or more bad apps making the phone unstable. The only way to find out that is to uninstall all of your 3rd party apps and reinstall one by one and use the phone a bit beofre you install the next one. - However, with the N97 it can be other things than apps too.
If you almost never turn off your phone, you should concider turning it on and off once a week to clear ram and possible other glitches.
I thought the N97 had decent music quality, but you might be talking about playing music through loud speaker? In that case there isn't much you can do as the phone's loud speaker system is stuck at a sound which mostly are on the treble side. Less mids and almost non bass at all. I guess the bass you're looking for with your trance, is impossible for the speaker to recreate.
If you somehow have issues with it through headphones I will concider looking at a pair of new ones. Check out google and gsm arena if you can find some numbers on what output signal the n97 has and buy some headphones which the n97 is able to run (Possibly not too heavy ones).
There are also small external speakers which you can get for mobile phones and mpr3 players etc which is powered by battery, small and are easy to carry along. If you want to connect the n97 to larger speakers through the jack, there are cheap external amplifiers to get. Those are made for small music players etc which do not deliver much rock'n roll themselvs.