Mmm.. I would have gone for the preamp first as it's earlier in the chain . TBH it only takes a couple of minutes to swap the fuses around anyway . You would also be surprised at how a DAC will improve with a better power supply . My Denon DAC improved markedly when I substituted the wallwart with a quality linear PSU , so I would try it there too ( unless you like to use the properly rated fuse for each piece of equipment ) .
Regards
Brian
Sell your cleverness and buy bewilderment . (Rumi )
Korus Computer Audio music server
JustBoom DAC . HRT Musicstreamer 2
Amplifier : Sony TA FB740R
Speakers : Tannoy 637
Interconnects : MS Audio / Klotz MC5000 .
Speaker cables : Western Electric 16AG