what is it you are after? modern furniture? then only ikea and you'd have to go to SD to really see the stuff as they often have stock issues: they may not have a piece in a particular fabric or colour, for instance. the staff there is super helpful, i was very impressed. a girl who served us did not want to speak any english but she understood everything i said and helped with vocabulary (i spoke to her in spanish but talked with miesposo in english, like we always do).
for electrodomesticos there is a big choice: gonzales, corripio, la sirena, L&R comercial, francis muebles. all places will offer a discount when paying in cash. but i do not need to remind you that, i think, you are dominican and know that
if you want wood some furniture is best made by hand by ebanista: beds, tables, libreros and so on. you will get exactly what you want in the exact wood you want. cheap too.