Hi Morris,
As per the previous suggestions, shared hosting would not be a good place for an E-Commerce website. Particularly not if you have 500+ products and a steady stream of traffic on a daily basis. Shared hosting is fantastic for small business websites, blogs, etc - but when you come to selling products - it's simply not reliable enough, especially as you grow!
I see that you're using OpenCart for your E-Commerce website, which is a great tool and although not quite as in-depth as Magento, it certainly doesn't come with the same speed issues "out of the box". The fact that you mention your page load times are 4.9 seconds is a little worrying, but you are on shared hosting - so obviously this contributes somewhat towards the problem.
If your website is still running slowly after moving to a new hosting package, I would suggest getting an OpenCart expert to look through the site and check if there are any issues affecting the speed. I can see that some of your images and CSS code could do with optimising for a speed boost.
You have a couple of choices with regards to hosting options....
The way we run things in my company, is that for any E-Commerce clients (who 99% of the time want to use Magento), we actually use a 3rd part specialist Magento hosting company to host their site. The benefits we have is that their servers are custom built to only run Magento, so there are not hundreds of other websites sharing the same server and the server itself is optimised for the E-Commerce processes. I don't know of a similar company that specialises in OpenCart hosting in the USA, but I'm certain there will be some available.
Your other two options will give you a little more control and they are either a VPS (virtual server) or a Dedicated Server. When looking for a company who offer these, it would be prudent to look for a company that offers a "managed" service. This means that if/when you experience issues, their support team will assist you with resolving these problems. Again, as a business owner selling products online, this support can (and likely will) prove vital to you in the future. Alternatively, if you have someone who can be the 'server tech' inside your organisation already, you can choose "unmanaged" and save a few dollars per month.
VPS (Virtual Server) - This is the cheaper of the two options. You'll be given part of a dedicated server, often with only a handful of other users on that particular server. The biggest benefit is that your website will be allocated more resources, meaning it will be faster in terms of data queries and displaying your content. If you go this route you should budget $20-40 per month for a good provider.
Dedicated Server - This is the best solution in terms of long-term, but the monthly fees are going to be a lot higher. Typically you'd be looking at $100-250 per month, depending on the server specification that you require. I'd suggest you'd be looking at the lower end of this budget, from looking at your website - unless you're trying to run 500,000+ products? 
With the VPS/Dedicated Server options, you'll be able to run multiple websites. So if your company grows in the future or if you decide to set up other websites in more niches, you will have the capacity to do this easily.
Finally, before choosing any host - ask them for some test websites that are currently on their servers. If they can give you examples of E-Commerce websites on similar packages/servers to the option that you're looking at, that would be perfect. I'm sorry that I don't have enough knowledge of the US hosting market to make specific recommendations, but you should certainly be able to find a lot of great reviews from real users online.
All the best with finding a suitable host for your business and I wish you every success for the new year!
Regards,
Matt Davies