You could use "Search in Phrases" to search for welcome_to_the_x (Search For Text = welcome_to_the_x, "Search In..." = Phrase Variable Name Only). When you find it, press "Edit", then enter a new phrase at the bottom and press "Save".
The first line comes from the options, in the adminCP Settings, Options -> Site Name / URL / Contact Details -> Forum Name.
The other thing you could do is just change the lines to read the way you want it to, like:
Code:
<h1>kh-mediaflare.net Forums</h1>
<p id="welcomemessage" class="description">Welcome to kh-mediaflare.net</p>
I guess the downside to the second way is if the phrases are used any place else they won't be changed.