This is a more elegant solution than P-clamps:

http://www.amazon.com/Sunlite-Bicycl...2836362&sr=8-1

I just got one of these and it works great! Just measure your seat tube to make sure you get the right size. My frame is aluminum and I needed the larger one.

To the OP. The 2008 Trek Portland is an outstanding commuter bike. Light and smooth rode. The disc brakes tend to warp and need constant babysitting. You' may need full fenders also. Other than that, it's a great bike.

Like a couple have said, try cutting down on what you carry. Leave the shoes and belt at work, maybe, or some other things that you can leave there. Leave as much as possible at work, and carry only the essentials in.

I also do a 16 mile each way commute over hilly terrain, and I get by with a backpack. I understand everyone's circumstances are unique, but there is probably a way to cut down on what you have to carry.

Sounds like I would keep & use the bike I already had. For additional support for a seatpost rack, you can go to a hardware store & get some angle iron, about 3/4" x 3/4 " that has round or elongated holes in it. Cut & fit one end under the side " lip " of the rack using stove bolts, & the other end can fasten by opening up the end, where it looks like a " U " & slip it behind the wheel nuts/skewer. You can then add panniers, baskets, to the rear. Hope I described it good enough.

But why compromise? The OP is in the market to buy a new bike, so he may as well get one that will take a sturdy rack/trunk bag and/or panniers.

Personally, I don't mind loading my work clothes/shoes/towel in my trunk bag/panniers every day. It's one less thing to think about (now what's at work and what's at home again?), and I view the extra weight as a training aid...

Also, they're not a good idea with panniers.

OP, backpacks suck in the wind. Learn how to travel light, get a used cyclocross bike that will take a rack and mount racing tires on it. You'll be plenty fast.

Topeak has a seatpost mountable rack. Roll your stuff into a bag or something, and put it on the back. You're done :)
This way you'd save yourself a ton of money, and you get to keep your trusty Jamis.

They are good with panniers.

http://i256.photobucket.com/albums/h...ide/90East.jpg
http://i256.photobucket.com/albums/h...0502mitour.jpg

I bought a topeak seatpost rack and matching trunk bag in 1999 and I still use it every day on my commuter. Works well for me. My current bike has a carbon fiber seatpost and the rack has never damaged it. I keep the clamp tight on the seatpost and don't have any problems with the rack sliding from side to side. Since it only takes a few seconds to put on and take off, I leave the rack at home on my weekend rides.

I have no racks on my Raleigh, which was my primary commuter for a couple of years. I bought a seat post rack and a small pannier from Performance. It was exactly what I needed to carry my clothes, minus shoes to work. I left shoes there. Now I have a cross bike, with a big rack. I can carry anything.

Update from the OP

I discussed all of what I learned here with my wife. Big mistake. Thanks to all the posts showing me how I could use my current bikes, my $2000 budget got usurped by the house painting and new garage doors budget.

I am now going to try one of 2 options. First, I took an old set of mavic classic elite roadie rims and put some 25's on the front of my Trek 7300 but had to stick with the current rims for the back due to drop out spacing of 135mm. I put 28's on the back. I ripped off the riser bar and heavy adjustable stem and but a mountain bike stem and light weight bar on the trek. I changed out the seatpost and heavy seat for lighter left overs from my parts bin. Also, I took off the pedals with cages and replaced with some SPD clipless pedals I took off one of my mountain bikes. All together I may have dropped a few pounds from the pig and decreased rolling resistance with skinny tires. I will try a commute to work on tuesday. No money spent so far on this, just using parts from other bikes I have.

If I don't notice a significant increase in speed I will have to go with one of the options for mounting a rack to the Jamis. Thanks again to everyone although I shouldn't have shared the info with my wife:cry:

I do 19 miles each way on a Salsa Casseroll. Stock 105 build. I've added a rack and Dinotte 400's front and back. Ride 28mm Conti Gatorskins at 120 PSI. It is a comfortable, well mannered ride, and deals well with the sketchier bits of my route. I dream of something lighter though.