Hello Josh and welcome to the "club"
The debate between a 6" Achro vs. a 6" Newt (or SCT for that matter) is an often raised question.
I'd like to point out that firstly, a 6" REFRACTOR is a heavy and bulky object. To wit, it will be effortful to deploy it to do terrestrial viewing unless you are always viewing from 1 fixed spot. Of course, a 6" Newt is a no-go unless you are able to read upside-down
Also, the scope itself weighs 7.5kg, without associated rings, accessories and eyepieces so unless your tripod or Alt-Az mount is heavier duty, you will find that it will strain the system.
Regarding chromatic aberration: a fast achromat is not really meant to look at bright objects such as the Moon, Jupiter or bright stars like Vega or Sirius, to name a few. However, for dimmer DSOs this is much less of an issue. Personally i think that sometimes CA makes stars look prettier because I sorta like the blur border that makes them really look like diamonds. Sometimes
I strongly suggest you look through one of these scopes, if possible, before deciding if the degree of chromatic aberration is acceptable for you.
a CG-4 is not really an ideal platform to image with such a heavy scope: The CG-4 may not be able to deal with the weight and the result is streaky stars, which are frustrating.
Regarding Orion vs. Celestron: Virtually the same with some minor design differences. Meade, Celestron, Orion, Explore Scientific, Skywatcher, , Antares, GSO, Astro-Tech, Stellarvue are all China made scopes so the lenses are mass produced to variable quality, although of late the quality has been fairly good. The main producers of such scopes in China are Synta (PRC), JOC (PRC) and GSO (Taiwan). Astro-Tech and Stellarvue are owner-operator shops in the USA who also do some QC on the units they sell so they are considered a step above.
The Orion 8" f/3.9 is a fine scope and will produce many fine images certainly at a beginning or intermediate level. Collimation may be an issue photographically but visually it will be relatively simple to do with a Barlowed laser (cheap - can be made for less than USD$60 and the barlow component can be used as, well, your regular observing barlow lens). I routinely take less than 5 mins to collimate my f/4.7 Truss-Dob very satisfactorily. What you will have to deal with, at f/3.9 is Coma. Lots and lots of it. To this end a coma corrector may be desirable so do factor that in your costs. These range from the cheaper GSO/Astro-Tech/Baader MPCC to the expensive Televue Paracorr.
Regarding suitable eyepieces: Its not true that you "need" $600-$800 Televue eyepieces for an f/4 scope. To start, Televue Plossls can be routinely had, used, for under $100 each or new for about $150 from the USA. Explore Scientific 82degree eyepieces start at USD99 and people have reported being very satisfied with them. Of course you can buy new Televue Ethos eyepieces for between $700-$1250 each but that would be a personal choice
Even if you did use lower end eyepieces, its the edges of view that suffer. Generally the center of view is well preserved in all but the cheapest eyepieces. To this end, its probably useful asking for specifics either here or in the cloudynights forums
So, what can a 6" see? I observe from a slightly darker part of Singapore in the North and with my 50mm Binos I can routinely see down to mag 6+ stars to the north but only Mag 4+ when looking south into the CBD's light dome. In my 4" Refractor I can expect to see at least Mag 10 stars (although they are faint - perhaps Mag 9+ for easy seeing) I can easily see the Orion nebula and sometimes the Lagoon nebula, not to mention bright planetary nebulae like the Ring and Dumbbell. In my 8" SCT (which has roughly the light gathering power of a 6" refractor due to reflectivity losses) I can definitely see down to at least Mag 11+, resolve Omega Centauri somewhat. Of course when we go for a short 2 hr drive up to Johor when everything is thrown out of the window: my 4" refractor there will outperform my 8" here. Hence perhaps the most important tool in visual astronomy is actually the ability to seek darker skies!
Personally I suggest that if you intend to go visual first, then get a dobsonian. An 8" will provide very decent aperture and locally Skywatcher (I'm not advocating the seller!) sells them for a reasonable price (or you can import from the USA but be aware shipping is expensive since they calculate by volume and a telescope is mostly empty air). You have your choice of computerized goto or not based on pricing. Then when you feel you want to delve into astro-photography, get a smaller 80mm or 4" refractor to start to minimise the effect of overloading your mount or higher magnification, which increases the camera shake caused by motor/gear irregularities in the mount or inaccurate polar alignment, which you can also use for daytime duties.