Can i setup Asterisk so everything stays at SIP level?

basically i want to setup an Asterisk server so that I have 2 outside telephone lines (from my own chosen sip provider) that once it is dialed it forwards to an internal “pbx” that has all softphones and strictly IP phones. So basically I should need no extra hardware except the Asterisk server and the IP phones that connect to the asterisk server via RJ45 or whatever, pull an ip and interface with the asterisk server.

Is this possible? cuz I see all this stuff about FXO and all these fancy cards and telephony devices when researching Asterisk and VOIP solutions and I am wondering why everything cannot just be kept IP all the way through

The only time you need those cards is either for A) If you want to connect to the PSTN or B) If you need a timing source for conferencing. You do not need any special cards if you want to have a pure VOIP solution.