OK let take the concrete approach.
You have two accounts each provides 3Mb/sec.
Let assume that each would yields Max. of 350KB/sec. Stable Download.
You can Download one or two files at 350Kb/sec. or 10 file at at 70Kb/sec. or any other combination of this nature.
However No single download would exceed 350KB/sec.
If you need more you would need to purchase your own backbone connections a s well a special server and server software.
The last time I look the software itself was in excess of $12,000.
A more viable solution is to find a provider that is selling a Cooperate level Internet Connections. As an example Road Runner offers a 6 Mbps download, 2 Mbps upload, 13 Static IP Addresses.
Do not feel bad, you are not alone, every week there plenty of guys that post similar threads thinking that they deserve getting the entire Internet traffic for themselves with entry level systems, unfortunately they have to walk away disappointed.
:sun: