What to do: upgrade amp or buy pre-amp

Im very curious what my spkrs will sound like if i changed to an Audio Research Ref 210 monoblock setup OR buy the Ref 5 preamp? Currently running media PC via transparent digital Spdif to wyred for sound DAC to Levinson 331 amp to Dynaudio C4 with REL G2 for low freq. So what would you guys upgrade? Ill most lukely pickup whichever piece i don't buy in the next 6 to 12 months but don't want to splurge all at once.