Recommendations for modest budget

2 years ago I bought an OLED and at the time paired it with an LG SJ9 sound bar due to space constraints.  Now I have a space that could easily hold any size 5.1 system so I'm looking to upgrade.  Trying to keep the budget modest, let's say $2k (not firm).  Any recommendations on where to start searching would be greatly appreciated.  I'm not expecting top of the line equipment with this budget but I would like something that's a substantial improvement over the sound bar.  Thanks!
Good idea to upgrade from sound bar.

I really like Marantz receivers, and your best value is buying last year’s model at 60% of retail when the new model comes out. I got the SR5012 for $600 (down from $1k) when the 5013 was announced. You may be able to now get the 5013 for a similar amount since I believe the 5014 is announced. The nice thing about these receivers (not that others don’t as well) but they do great with latest HT stuff but also have nice music streamers for 2ch audio via Tidal/Spotify/Qobuzz etc.

For speakers, maybe aim to spend about $300-400 on a sub and $1k-1.1k on the remaining speakers (left, right, center, rear surrounds for a 5.1 system, couple pairs of rears if you want 7.1). Of these, the L, R, and center are the most important, and I’d devote at least $800-900 of the $1k to those three, with the remaining $100-200 spread across the 2 or 4 rear surround speakers.

Some brands to look at for the three front speakers in that price range: NHT, PSB, Elac, lower end Martin Logan, Klipsch.

Not sure if SVS makes a $300-400 sub but if they do look at that. Sunfire SDS10 would do a nice job as well.

Others will differ but I think at this budget don't worry about cables much - keep it very cheap.  AmazonBasics-level stuff is fine and stock power cords.

Good luck.

At that budget, I’d check out for a receiver. Personally I’d want something 4ohm stable and with pre-outs (so you have the flexibility for upgraded speakers and/or to add a separate amp later if you want to). The Marantz SR5013/SR6013 are $500/750, respectively, and they are solid, well-featured receivers. At this price range, Yamaha is another that is often recommended. 

For speakers, the same site usually has decent Kef & Focal speakers in your price range. You should also check out SVS, which has good value speakers and subwoofers. Should be able to find a good combo for your price range with either. Don’t skimp on the center channel (it should be the same brand and model range as the front R/L speakers), but it’s fine to save money on cheaper surrounds. If you have room for and choose large tower speakers for the fronted R/L, then you can probably wait on adding a subwoofer until later. If you go with bookshelf speakers, then the subwoofer is more critical.

A few ideas...
Option 1: ($50 over budget)
Marantz SR5013 — $500
SVS Tower System — $1550

Option 2: (over budget by the cost of the surrounds)
Marantz SR5013
Kef Q series front R/C/L 
—Q750 towers — $1000/pair
—Q650c center —$500 (currently out of stock but should come back)
Cheap surround speakers of your choosing.

Option 3: ($250 under budget)
Marantz SR6013 — $750 
SVS 5.1 satellite system $999 (or upgrade to one of their more powerful subs)

There are tons of other options that will blow away a soundbar for $2k, but hopefully this gives you some thoughts and ideas to consider. It’s also definitely a matter of personal taste, so it’s always best to try to hear speakers before you buy if possible or get them from companies with decent return policies.

Finally, and I probably should have said this first, it’s important to think about how you’ll actually use the system. Do you listen quietly or loudly? Do you love that feel-it-in-your-chest rumble of the low bass frequencies or get annoyed by them? Movies and TV only or do you also plan to use it to listen to music?..if so, how... streaming, vinyl, CDs, etc and do you already have these components?  Several components to connect or just the TV? For under $2k you could get a sonos 5.1 system that would be nice for TV and movies and add the ability to separate out the surrounds to use on the deck or in other rooms when you don’t need 5.1... that’s definitely added value and a great option for many people, but it has limited inputs and the benefits of these and other “wireless” systems means you need a power outlet near each speaker and it’s not the best bang-for-the-buck sound quality vs wired options, so there are always trade offs to consider. 

Best set of luck!
Your $2K budget, is NOT adequate for a 5.1 system with receiver included. Simply being honest.

The tipping point is around 5K (not including cables or a basic power conditioner) for what you are considering. 10K ideally for a basic yet very good full 5.x.x system (which could also include a second sub and object channel speakers).

Aesthetics and setup of a 5.1 system are problematic AND you will encounter problems and costs you don't anticipate.

For your budget (negotiated price) consider this:

OR opt for a 2Ch system, for now, and build upon it when funds are available. This allows for very good speakers and receiver used (at $2K). Choose speakers that offer matching center and surround, etc. so you can add those at a later date.
I don't think that the OP is going to almost triple his budget and a decent sounding 5.1 system can be had for two thousand dollars, how do I know? Because I have one! Bought the speakers and sub used and grabbed a last year model of my receiver at a big discount because it was being replaced by a newer model.  Check craigslist for sub and there always seems to be a lot of home theater speakers on there as well.

Good Luck, TISH