This is just a passing thought that struck me earlier today. Patrick Seitz worked with Crispin Freeman on Hellsing Ultimate: II, as Luke Valentine where Freeman was Dracula, respectively. The English dub of II came out June 12th of '07, and DXC came out on October 23rd of the same year. Given that Seitz's Dracula (which IIRC is the first Castlevania role he did for the character, correct me if I'm wrong) sounds really close to Freeman's Alucard, the idea hit me that perhaps Seitz drew inspiration for the voice from Freeman's talents?
This is all just idle speculation. If I missed the answer in some interview, let me know.