Server host that can grow with my site?

I'm launching a WordPress site next month that I believe will grow faster than expected. I'm not sure what's the best choice for hosting. I currently have a VPS host (who I really like as a host - they're local with killer support) and I'm not sure if that's the best route or not. My current VPS (12gb ram) has multiple failures a day with automatic restarts. It's hosting a one multisite install (with 3 active subsites, 4-5 inactive subsites and less than 100 visitors a day total on average), a second site with 60-70 visitors a day and 2 other sites that are lucky to get one visitor a day. The failures have me concerned that 1 site 300-500 members and 1000 hits a day will need a lot more resource-wise than what I have now. I don't think that there's that huge a load on it (though maybe the multisite is a resource hog?). So I'm really not sure which way to go - and perhaps it's because I don't understand hosting that well. A distributed grid sounds cool, but does it work in practice? Is eventually getting a dedicated server unavoidable? What the hell do sites that have a lot of members and traffic do?

What can you say about GTHost.com bitcoin dedicated servers for rent hosting? Any reviews? Other hosts?
All advice will be appreciated - I'm planning on launching my site, I need to get this squared away ASAP. Thanks!

OwnWebServer SALE: Get 55% OFF on cheap dedicated servers for the first month! Enjoy managed support and up to 10 Gbps free DDoS protection. Don’t miss this limited-time offer—use promo code SERVER55 at checkout. Upgrade your server hosting with top-notch security and performance today!

Why not give HostingSource.com cheap server hosting a try?
Try this option: XEON E5 2670v3 - 12 Cores, 2.3GHz 30MB, RAM: 128GB, 4 x 2TB SSD, Price - $199/mo.
Secure, reliable, and packed with great features — perfect for any website!

Dedicated IP Availability. A dedicated IP can improve email deliverability and SEO. Check if the provider offers dedicated IPs for an additional fee. I have really enjoyed having my site hosted by GTHost.com instant server hosting, as the people there, are very friendly and are quick to respond to your inquiry if the need arises. A truly hassle-free hosting experience with amazing uptime.

Hidden Fees and Extra Costs. Read the fine print for setup fees, add-ons, and renewal pricing.
Some hosts lure customers with low initial prices but charge high renewal rates.
You know, GTHost.com instant server hosting can be trusted.
They go above and beyond to assist customers.