Modern amplifiers do not have any sound. They are transparent, and amplify the signal they are given. If you are dissatisfied, you should change the speakers. Those do have personality of their own.
I beg to differ as this is quite simply an altogether untrue statement. Most, if not all, modern amps certainly DO "color" the sound. In fact, most modern consumer amps suck sound-wise. If you really want hi fidelity you need to go "pro" or high-end "boutique".
Anytime a signal is passed through a solid-state circuit board, coloration will and does occur. How much it occurs depends on a lot of factors, including but not limited to the make of the amp, the class (type A, B or A/B), model, circuit design, type and quality of components used, etc. If there are capacitors, chips, transistors, resistors, or any combination thereof, coloration
will occur. Tube amps, of course, color the sound as well, just in a different way. They get a "tubey" type sound that some people prefer. The trick is finding an amp and speaker combo which, together, produces a character or color that you like. And that comes down to knowledge (or finding a good consultant who really knows his/her stuff), trial and error (not an option for most) or just doing a ton a research, review reading and hoping for the best.
Addendum: If you are playing your music from a music software library like iTunes via a computer (Mac or PC), then the single most important piece of gear you can upgrade to for improved sound is your sound card. Depending on the type of card and its configuration, if you then couple that with a high-quality external DAC unit, it will change your world forever. I have a Lynx AES-16e sound card (retails for $650) that I have been extremely happy with, which I run the signal out of (digitally) to a Mytek Stereo96 DAC (48/96kHz D/A converter), then directly into a pair of powered Mackie HR824 reference monitors. The Mytek goes for approximately $1,000 new (if you're lucky you can find a used one for $500 to $700) and is hands down my absolute favorite DAC available on the market today (extremely smooth, transparent, clear and accurate from 5 Hz to 20 kHz). I worked as a professional audio engineer here in Nashville for almost 30 years and owned my own mid-level professional recording facility for nearly 20, so I've had a lot of time and opportunity to hear and/or use just about everything that's available on the market.
One day I will substitute new speakers into my setup but, until then, the HR824s sound great.