With the 598, you do not need an amp to enjoy it. Love Keens! Nothing very loud, but nonetheless I wouldn’t use it at night if you’re in an apartment like myself. Minimal features. There will come a day that you wont need the extra length of laces (so remove them, and relace). im in love with these, I ordered a size 10 in royal blue my favourite colour and since I havent had the opportunity to use them due to covid, Ive been wearing them around the house for cleaning to add little pep in my step. My foot size is 10. The lock mechanism that you pull up after attaching the pump to the tire doesnt work/hold and it seems to only be letting air out. I hooked up a POWERTEC 70198 2-1/2-Inch Flexible Dust Collection Hose 36-Inch Long into a 2. With XM4 the bass sounds mixed, muddled and boomy.