Based on my experience with the DTs... I would argue for upgrading the Speakers first. I know there are plenty of DT fans out there, and I mean no disrespect, but Sound Quality is not what I thought of when listening to those Speakers.
Electronics (Amps, AVRs, AVPs) are not likely going to give you any sense of SQ improvement unless you are coming from a 10+yr old lower grade product. An upgrade there should be due to needing updated technology, but based on the state of todays AVRs and AVPs, waiting (if possible) is advised until manufacturers get their tech sorted out.
Which Arendals were you looking at?