You definitely need to take care of your DAC/preamp first before upgrading the speakers. Your Teac UD 301 DAC/preamp just can’t do justice for the rest of your setup and system. I recommend either the PS Audio DirectStream DAC with Perfect Wave ll or the Classe CP 800 stereo preamp/DAC. Either of these will be a big step up sonically from your Teac UD 301 DAC/preamp and will elevate the overall performance of your setup/system to the next level. Even the Benchmard DAC2 or DAC3 will be significant improvements from what you have now. Your Teac UD 301 DAC/preamp is fine for just playing background music but not for critical listening.
Your Vandy speakers are awesome IMO and you can always change up speakers anytime you wish but first you will have to upgrade your upstream component(s) (DAC/preamp) first for critical listening.
It all comes down to personal preference and taste and musical tastes when it comes to speaker choices. There are countless options out there.