There are a lot of hosts that could meet your needs for that price range. However, like Dactyl stated, no hosts can repsond with offers for you here.
If you are starting a small forum, you may not need 50GB of bandwidth right off the back. You could start small and when you need more resources just upgrade.
Hope things work out for you. Make sure you research your new host and read the reviews on the page. You may also want to send in test support e-mails. One during the day, and one at night. See what type of turn around time they have.
4GB or more space
50GB is probably enough transfer
at least 5 mysql database
subdomain would be nice but not required
price range : max 8/month
I believe that in the beginning you'll be fine, but once your forum starts to grow and you'll have a significant number of simultaneous users online, even if your site won't be using all those 50GB, you might be asked to move due to high server resources usage (CPU and memory), especially on a budget host like the one you're looking for.
Just a little something to ponder on and properly take into consideration.
Since you are just starting out, and expect a year or two till you need this much resources then maybe if you look for something smaller you could save for those 2 years and then when you need the space you can upgrade to a better plan and have more money saved to spend on it. Just a thought.