95% of my fishing is done at Big Spring, Letort, Falling Spring and Green Spring. I use an 8 foot 4 weight Winston WT on these streams in all but the windiest of conditions so I can tell you with 100% certainty you won’t go wrong with a medium action 8 or 8.5 foot 4 weight as an all purpose rod for these types of waters. I’ve even used my 4 weight on the Delaware but in no wind conditions. I fish everything from small midges, to tandems to heavy (#6) streamers with no problem. The rod can cast for distance when needed (about 50 feet comfortably), has feel for close up delicate work, protects fine tippets, and has the strength to stop big ones when needed.
The Sage Flight is really a nice rod for the money. I’ve cast the 8 foot 4 weight model and it’s really a nice rod. It feels almost like the Z-Axis just a little bit softer.
As for the Sage TXL, I’ve cast the 6’-3” 3 weight model and while it is a nice rod and casts well, it’s really a specialty light weight rod. Granted the one I cast was shorter than what you are talking about but just based on the light weight design of the TXL series I don’t think a TXL 4 weight would give you the same flexibility as a Sage ZXL, Flight or even Z-Axis. I’d really test cast the crap of the TXL to make sure it does what you want, as dropping $550 on a rod only to find out it’s not what you want wouldn’t be a good thing.
Personally, for an all purpose rod for the waters you mentioned I’d either go with the Flight for less money than the TXL or drop an extra $100 or so above the price of the TXL and get the Sage ZXL or a Winston WT. You also might want to try the Winston Biit and Biix, as well as the Sage Z-Axis. Another one to consider is a Scott G2. Although I only cast one once, (9 foot 5 weight G2), I was impressed with how it felt. The Biit is basically the WT except made out of boron instead of graphite and the Biix is Winston’s fast action boron rod. The Z-Axis is a really a nice fast action rod that performs extremely well in close but personally I think it is a bit better suited for waters where your average cast will be longer than on the waters above. That’s just my preference, however but I really don’t think you’d go wrong if you went with a Z-Axis – it definitely would give you more flexibility on larger waters than the ZXL, WT or Biit.
One option you might want to consider is getting a high end used rod. You can find $650 rods in great shape for very low prices if you look around. Check out www.codella.com. (Len Codella used to own Thomas and Thomas and is very reputable). Although not purchased from Codella, my Winston WT 4 weight was purchased used for $225 and you could hardly tell it was used except for a little palm dirt on the cork grip (big deal). Even though I don’t have a warranty on it, if it breaks and costs me $200 to fix it, I’m still over $200 ahead from buying a new one.