Agree.
Placement overall starts with the Mains. After that, you have to extend that placement to the other Speakers in the Bed Layer. You should never even think Atmos unless you can get a very good 5.1 or 7.1 layout dialed in.
In support of Bill's comment, that Sub is definitely a weak link. My own personal feelings about B&W aside, your focus should always be on a proper 2.1 setup first. That LFE channel is really worth considering a proper upgrade.
After that, the next most important step is making certain you've got a great Center.
Surround and Rear Speakers do not need to carry the full load that the Front 3 do. You don't want to skimp, but they don't need to be a major drain on the budget.
If you upgrade, you can also move good Speakers around, assuming you are adding better up front!
Understanding the Dolby PDF file (not the cool little overhead drawings you often see online) is a must. This takes you from basic 2-channel all the way to 9-channel bed layer setups and how to plan for atmosphere if you want it.
From there, however, it is really all about angles when you place your Speakers. If you can get the Angle right, you will benefit from a good sound field.
Even mediocre Speakers can be made to work in the proper setting. From there, your upgrade path becomes more linear as you can target the weakest link each time you choose to invest in your system.