If upgrading speaker. Typically you want to find speakers that captivate you… ignoring requirements. Speakers are very important to your enjoyment and if they don’t captivate you it is unlikely any amount of changes in electronics is going to help that.
While typically 8 ohm speakers are “easier to drive” but there are so many variables… I wouldn’t let it drive your choice.
If you chose planar speakers (electrostatic or ribbon), they require a lot of power (current). Then you will have reason to pause and consider what other changes you may have to do.
Best find speakers that sound great to you… then see if your electronics are up to them.