Speakers make the most difference to the sound quality. They have a very long life (decades) and are harder to replace due to size and weight. AVR’s get outdated every few years, due to new standards and technology advances. I would put most of my money towards better speakers now - especially the front three speakers, and skimp on the AVR and surrounds.
I would spend most of my budget on the front three speakers and a decent sub right now. I like towers for the mains, but good bookshelves could work too. Note towers generally require much less power than bookshelves. Either get super cheap surrounds (even if from a different brand and not timbre matched) or skip the surrounds. Upgrade the surrounds at a later time as budget permits to align with the mains. Also add a second sub (for more even bass) at a later time.
Get something like a Denon 3600H/3700H for now, which is more than adequate for your needs. Add an external amp down the road for more power.
Unless you’re getting an exceptional deal on the SVS speakers, there are other speaker brands that I would look at. Salk, Ascend, KEF, Revel, Focal (9xx Series) are some good options to consider.
These options may be pricier than SVS, hence the suggestion to save money on the receiver and surrounds.
I really like Rythmik for the sub.
