High Availability and NAS

First thanks to anyone that replies and offers guidance, even just links for a do it yourself dummy would help me some.

I run a small business server setup, all of ten employees. Nothing fancy, file server, DC, couple application servers and a terminal server. I have them all running on VM's with two VM hosts with just the free esxi and has been this way for several years now.

We've reach a point where downtime due to hardware failure is not something the business can tolerate any longer. As such I'm looking at what I need to upgrade to achieve that goal. About a year ago I reached out to some vendors and it wasn't in our budget then. I've reached out again with a new budget only all the answers seem to have changed to vastly increase my spend and I'm not sure if the current bit is an 'upsell' or truly needed.

Last year I was directed to the vsphere standard and a NAS for around 400. This year I'm directed to the essentials plus kit and a nas for several thousand or it won't be 'good enough' to run any vm's. It appears the essentials plus kit is indeed required for the high availability on a couple server with 2 cpus as the best pricing option. So I guess the question is what's my best options to get the high availability I need while keeping costs down.