Improving on the N130 is relatively easy and doesn't have to be expensive. The Node Nano can get the job done.
If you want to take things to another level—especially in terms of soundstage performance—while staying under $1,000 on the used market, consider the Holo Red.
If you can stretch the budget a bit further, to around $1,500, consider the Volumio Rivo with an LPS or the Innuos Zen Mk3.

