Tread Lightly Franck, Buyer BEWARE
Maybe host one or two sites for a while, see how things go, and what kind of support you get.
Use some domain tools and whois see how many sites they have on the servers IP.
Like So:
Server Data
IP Address: 216.65.1.131
IP Location: United Kingdom - Liquidnet Ltd
Blacklist Status: Clear
SSL Cert: secureworldpay.supremecenter.com expires in 518 days
Website Status: Active
NS History: 3 changes. Using 3 unique name servers in 4 years.
IP History: 2 changes. Using 2 unique IP addresses in 3 years.
Whois History: 16 records have been archived since 2005-03-11
Reverse IP: 3,781 other sites hosted on this server.
Do some searches to find some actual customer reviews...
Hosting companies come and go and I have seen so many horror stories.........
Like Stephen says:Just speaking from personal experience - quality is better than quantity when it comes to hosting.