About your songs:
1) About first one, I liked it somehow better, cause I imagined this could work very good for long awaited intro for Nexuiz (gib splashing, fast movement, various explosions, skill-frags - generally showing that Nexuiz is very fast and very fun).
2) Yet second would be good as a general menu background one (having slower, more ambient but still energetic feel).
What I have always thought about nexuiz music, that it always lacked aggression (nexuiz is gib splashing ever lasting carnage, don't forget

) and industrial beat (that's why so many people like gasoline_powered because of scorp's music cause it gives map the feel).
Now about the problems: for songs to be acceptable for nexuiz, songs should be in ogg format (mp3 is patented technology). If your sounds would be accepted (in intro form or not) maybe some transition would be required from the first to second. Currently it's starts quietly.
The whole thing could be done smth like:
loading -> nexuiz intro (by kojak, cuizi, whoever is making ...) -> welcome to nexuiz -> menu sound. Intro video could be skipped by simple mouse press. Don't know what others think about it.