Hi robert -- welcome to the forum.
Any of those methods CAN work. I've had some success with them all, and I've had the most success by using combinations.
The key is knowing your target audience very well and being both precise and creative in reaching them. I'd also suggest having a very exact, measurable purpose for the site, so you can tell when you're succeeding.
If you don't have a big budget, you need to work smart! Here's some of my hard learned lessons:
1. Target the RIGHT keywords for search engines - it makes a big difference. We have an entire Keywords Forum, full of good information about that right here.
2. Avoid common email campaign pitfalls (Where did that distribution list come from? How good is your Subject, Body copy, and Call to Action?)
3. Viral marketing can be slow to start, but the long term results it can bring are quite good, because the market is pre-targeted for you.
4. Press releases are probably the toughest place to get results. Mostly the press will just yawn at an ordinary announcement.
But if you have a catchy angle, then you may catch a few good results. The job is to give the press enough "meat" to write an article from, or even have the job done for them. But avoid standard "marketing speak" -- that's just wasting your time and theirs.