which speakers should I buy?

contact hifibuys in Atlanta. They do custom installs with systems that specifically designed for outdoor audio. 

   I assume by "patio" you mean open-air outside space.  If not, forget what follows.  I'm in CA so mine is set up year-round.
  IMO, outdoor listening is quite unlike indoor listening -- where reflections, room configurations, carpets, drapes -- are mostly irrelevant to out-door listening.  I've experimented with several approaches over the years. I hauled floor standers and subwoofers outside for parties, tried multiple speaker arrays for a surround experience, and finally hooked up a pair of ancient 60 Hz Henry Kloss  "Cambridge" outdoors to an Alexa and digital amp for the pool and spa in my latest home.  
  You can't expect detail like you do indoors. Nature's concert venue provides a broad mid-range with adequate treble (not shrill at all)  and surprisingly acceptable bass.  Be mindful that your neighbors will appreciate not having you select their music for them.  
  So, I suggest you start with an inexpensive set of outdoor speakers (and a spool of inexpensive speaker wire), then experiment with multiple heights and placements.  I'd use an existing lower end amp or receiver and a voice controlled music source for several listening positions.  If you want more, then you already know why and how.  

I would have to say yes...you should.

Yes, outdoor open space with a house on one side and basically forrest surrounding 2 acres of grass. 
What about JBL professional PA speakers? Also electro voice speakers seem interesting. Would those sound horrible if I’m used to Hi End? 
I would prefer not to use an amp and speaker wire. But will do so if absolutely necessary. I have a few amps and preamps laying around. 

What about JBL professional PA speakers? Also electro voice speakers seem interesting.

A horn will work very well, JBL, and Klipsch both have great SQ along with being tough. What do you see when its live, outside? J arrays usually, and  2 or 3 way horn arrays...Behringer, JBL, Electro Voice, BG, and a hole slew of PA box guys,,,,GREAT Onboard Full Range amps, duno...Class whatever on the amp,  bluetooth, and no wires.  I suppose a power cord is ok? LOL

Regards