Shared vs. Virtual, how many users can they handle a day?

[Dekard]

I've got a site, www.overclockingwiki.org that I'm promoting heavily and traffic is growing. I'm concerned that eventually I may have to switch to a virtual server but I wanted to know what traffic levels could be supported on the shared servers.

Here's some traffic stats.

Summary
Reported period Month Nov 2006
First visit 01 Nov 2006 - 00:33
Last visit 24 Nov 2006 - 08:53
Unique Visitors 3425
Number of Visits 4051
Pages(1.18 visits/visitor) 45284
Hits (11.17 pages/visit) 147239 (36.34 hits/visit)
Bandwidth 1.12 GB (290.87 KB/visit)
Traffic not viewed *
4831 5086 25.38 MB

So far performance of the site has been good, except a few hours on November 13th when traffic went through the roof after a front page link on a major website. I saw a 11x increase in daily traffic and an hourly increase of significantly more than that. The site was quite slow then but considering the heavy load I'm not complaining.

[sgforumadmin]

From the numbers you gave, your site is still suitable for shared hosting. Those 4,000 or so visitors for 20 days are normal for a website on a shared server. Unfortunately, we cannot give you exact number of visitors/hits/bandwidth that set the limit. If that helps, 40,000 visitors will be too much. Also, you have already felt the effect of growth - the bigger the site with more simultaneous visitors, the slower it will get.

[Dekard]

Ya, I had 1300 unique visitors in one day and for a while the site was nearly unreachable... I'll keep on eye on traffic and performance. I just wish SG had a middle step, its a big jump between 4.95 a month and a VPS in price.

[Dekard]

A change was made to the forum. I added a phpbb forum by means of fantastico. The bandwidth usage increased quite a bit since the forum pages are larger than the wiki's but I'm no where close to using 1% of my bandwidth a month.

Would a combo wiki = phpbb forums change the number of daily users I could reasonably handle on a shared server?